John Ewbank https://johnewbank.co.uk/ Writing on energy, heat pumps, engineering and economics, with the working shown. https://johnewbank.co.uk/assets/share-card.png John Ewbank https://johnewbank.co.uk/ quarto-1.6.42 Wed, 21 Oct 2026 23:00:00 GMT How much do ACs increase the urban heat island effect? https://johnewbank.co.uk/how-much-do-acs-increase-urban-heat-islands/

Without the hype

There has been a surprising amount of chitter-chatter recently about whether air conditioning heats urban environments and makes the urban heat island effect worse. What is especially amusing about many of these arguments is that they often fail to understand how air conditioning actually works, and they also tend to ignore some fairly basic thermodynamics. Fortunately, there is a relatively easy way to think about it.

An air conditioner does not magically produce huge amounts of extra heat. It moves heat. During cooling, the outdoor unit rejects two things: the heat removed from inside the building, and the electrical energy used to run the compressor and fans. The important point is that only the second one is really new energy being added to the urban system. The heat removed from inside the building was already in the city. It was already in the air, the walls, the roof, the floors, the furniture, or on its way into those things. The air conditioner moves it from one place to another. It does not summon it from another dimension.

For a properly installed split air conditioner, during cooling in the UK, a rough figure might be that the compressor uses about one unit of electricity to move around four units of heat. So if the system removes 4 kW of heat from inside, it might use about 1 kW of electricity to do so. The outdoor unit would then reject about 5 kW of heat, but at the city scale, the key addition is not 5 kW. It is the 1 kW of electrical energy, which eventually becomes heat.

This is because the 4 kW of heat was already in the system: it was going to make its way outside whatever happened.

So let us try to put some rough numbers on this. A decent split air conditioner in a maisonette or flat might use something like 800 W of electricity while running. Obviously this varies enormously depending on the size of the property, the insulation, the temperature outside, how cold people set it, whether the unit is correctly sized, and so on. But 800 W is good enough for a rough estimate. London has around 4 million dwellings. If every one of those dwellings were running an air conditioner using 800 W, the total electrical power going into air conditioning would be 4 million × 800 W, which is 3.2 GW. To be generous, round that up to 4 GW.

That 4 GW is the extra heat being added to the city by the air conditioning. Not 20 GW, not 50 GW, not some magical enormous number. The additional heat is the electricity used to run the machines. So is 4 GW a lot? Well, it depends what you compare it to. The land area of London is about 1.5 billion square metres. Around midday in summer, solar irradiance in the UK might be somewhere around 800 to 1,000 W per square metre. Not every square metre is flat, unshaded, or receiving maximum sunlight, but for a back-of-the-envelope calculation we can use 1,000 W/m² and then account for reflection using albedo.

Urban albedo is complicated, because London is not just tarmac and roof tiles. It has parks, trees, water, light surfaces, dark surfaces, shaded streets, glass, brick, and all sorts of awkward geometry. But suppose we use an albedo of 0.25. That means roughly 75% of incoming solar energy is absorbed. So 1.5 billion m² × 1,000 W/m² × 0.75 gives about 1.125 TW, or 1,125 GW. Compared with 4 GW from the electricity used by air conditioning, the absorbed sunlight is hundreds of times larger. This does not mean air conditioning has no effect at all. It means that if we are talking about the energy budget of a city, we should keep some sense of scale.

Obviously this is a simplification, but it is a simplification based on the physics of how these units actually work. If you walk outside in a city at night and put your hand on a dark road, you can feel the heat coming off it. That is not an air conditioner. That is solar energy which was absorbed during the day and then stored in the urban fabric. Realistically, the urban heat island effect is largely a consequence of low-albedo surfaces and thermal mass: dark roofs, dark roads, brick, concrete, asphalt, and all the other materials which absorb a lot of sunlight and then release that heat slowly later on.

You can go and sit on dry, crusty grass in a park in summer and it might not be especially pleasant, but it usually does not feel like sitting on a hotplate. You are not going to casually sit down on a black road surface that has spent all afternoon absorbing and retaining an enormous amount of heat. So if you wanted to reduce urban heat island effects, the most obvious place to start is not shouting about air conditioners. It is the surfaces.

For example, you could look at adding reflective pigments or lighter aggregates to road surfaces. Obviously you have to be careful with this. You do not want to blind drivers, create glare problems, make road markings harder to see, or produce surfaces that are unsafe in wet conditions. But fundamentally, the more incoming solar radiation you can reflect rather than absorb, the better your outcomes are likely to be.

Back to top ]]> Heat pumps Environment https://johnewbank.co.uk/how-much-do-acs-increase-urban-heat-islands/ Wed, 21 Oct 2026 23:00:00 GMT Interactive SCOP Analysis and Cost Comparison for Heating Systems https://johnewbank.co.uk/scop-heating-cost-calculator/

Without the hype

Compare what it costs to heat a home with different systems, from an old oil boiler to a well-installed heat pump. Put in your own prices and heat demand. Electricity and gas start at the Ofgem price cap for October to December 2026, or its average over the last three years, and heating oil at the UK average market price on 22 October 2026.

What is SCOP?

SCOP stands for Seasonal Coefficient of Performance. It’s a measure of heating system efficiency that takes into account seasonal variations in performance. SCOP represents the ratio of heat output to energy input over an entire heating season.

Understanding SCOP: Input vs. Output

  • SCOP is calculated as: SCOP = Heat Output / Energy Input
  • Higher SCOP values indicate better efficiency. For example, a SCOP of 4 means the system produces 4 units of heat for every 1 unit of energy input.
  • SCOP of 4: 1 unit of input energy produces 4 units of heat output (high efficiency)
  • SCOP of 2: 1 unit of input energy produces 2 units of heat output (low efficiency)
  • SCOP of 0.5: 2 units of input energy are needed to produce 1 unit of heat output (very low efficiency)

Your figures

Energy prices

Your home

Compare

Installation costs

Heat pumps

Each heat pump’s cost can be typed over; moving either slider puts them all back to the formula.

Other systems, installed new

Electricity and gas start at the Ofgem price cap’s average unit rates for Direct Debit: the cap now (October to December 2026), the average of the last three years of quarterly caps (January 2024 to December 2026), or the forecast for January to March 2027 (30.28p and 9.76p, from Cornwall Insight on 30 September 2026). Forecasts move as wholesale prices do; Ofgem announces the actual January cap in late November. Your own tariff may differ by region. Heating oil isn’t capped, so it is always today’s market price: 118.5p a litre (BoilerJuice, 22 October 2026) at 10.35 kWh a litre. Standing charges aren’t included. If a heat pump lets you give up gas altogether, you also stop paying the gas standing charge, about £108 a year at the October 2026 cap.

What a heat pump saves each year against , by SCOP

The dots are the heat pump installs in the table. Below the zero line, the heat pump costs more to run than the baseline. Change the baseline, prices or heat demand above and the chart follows.

-year CO2 emissions comparison

-year cost comparison

Interpreting the Results

  • Darker shading in the cost column means a higher cost, and the baseline system is in bold.
  • Compare the ‘kWh input for 1 kWh heat’ column to see how much input energy each system uses.
  • The ‘-year cost’ column shows the estimated operating cost for each system based on your inputs.
  • ‘-year savings’ shows the potential savings compared to the selected baseline system.
  • ‘Payback time’ indicates how long it would take to recover the installation cost based on the yearly savings.
  • The ‘-year CO2’ column shows the estimated carbon emissions for each system.
  • The savings chart shows the SCOP a heat pump needs to beat the baseline on running costs, and what each step up in SCOP is worth.

Emission Factors Used

  • Natural Gas: kg CO2/kWh
  • Heating Oil: kg CO2/kWh
  • Electricity: User-adjustable (default 0.131 kg CO2/kWh)

These are the UK government’s greenhouse gas conversion factors for 2026. The electricity figure is the average for grid power in that year’s set, down from 0.177 in 2025 as the grid has decarbonised.

Back to top ]]> Heat pumps https://johnewbank.co.uk/scop-heating-cost-calculator/ Wed, 21 Oct 2026 23:00:00 GMT Why won’t my air-to-air heat pump maintain a stable temperature? https://johnewbank.co.uk/why-wont-my-air-to-air-heat-pump-maintain-a-stable-temperature/

Without the hype

Many air-to-air (A2A) heat pumps struggle to maintain a stable room temperature because the temperature sensor is often found inside the wall-mounted indoor unit. This is usually high on the wall, and is prone to reading a warmer temperature than other parts of the room and therefore the units often shut off prematurely. At low fan speeds, poor air circulation can also cause cold spots and inconsistent temperatures.

Inside an air-to-air indoor unit, with the room temperature sensor circled in red just above the heat exchanger coil.
This is an example of a temperature sensor located above the coil, this can cause the unit to overread the room temperature and shut off prematurely.

You probably won’t be surprised to know that many installers and manufacturers pretend this isn’t an issue. Which might be why you are reading this.

Before buying additional controls, try increasing the fan speed and angling the vanes downwards. If your room is small then some people find that blowing horizontally also works well. Blowing downwards helps to mix air and often improves temperature distribution. If you do not find that comfortable, nor want the additional noise or air movement, then you will need an external temperature sensor.

Some manufacturers, like Midea, put an additional temperature sensor in the remote control.

A Midea air conditioner remote control, front and back, with a grille at the top for its built-in temperature sensor.

Midea remote controller – top right grate on is the temperature sensor location.

Few manufacturers support manufacturer-supplied wall-mounted controls with thermostats.

Third-party options come in several forms:

  • ProtoART offers advanced control and monitoring. Installation is relatively involved, and you use a separate app instead of the standard remote. However, it can integrate with Home Assistant and devices such as window sensors, allowing the heat pump to switch off when a window is opened. With some units, including those from Mitsubishi Heavy Industries, it can also display detailed information such as temperatures and compressor speed. This makes it particularly useful for technically minded users.Es Tresidder has fitted one to his Mitsubishi Heavy Industries unit and reports that it has improved his experience. [https://www.highlandpassive.com/a2a-remotethermostat/%5D
A small digital temperature and humidity display beside a ProtoART board with a green cable for connecting to the indoor unit.
ProtoART connector and temperature sensor.
  • tado° Smart AC Control is probably the most straightforward option for many UK users. It controls the heat pump using infrared, like the supplied remote, but measures the temperature near the controller rather than inside the indoor unit. https://amzn.to/4rPZzdn

The tado° Smart AC Control, a white controller with a display, on a stand.

The tado° Smart AC Control.
  • Mysa Smart Thermostat is another well-regarded option, particularly for users in the US: https://getmysa.com/

The Mysa smart thermostat for air conditioners, a white wall unit with touch controls.

The Mysa smart thermostat.
Back to top ]]> Heat pumps https://johnewbank.co.uk/why-wont-my-air-to-air-heat-pump-maintain-a-stable-temperature/ Thu, 24 Sep 2026 23:00:00 GMT Why Nuclear Power Can and Will Get Cheaper https://johnewbank.co.uk/why-nuclear-power-can-and-will-get-cheaper/

Without the hype

Building nuclear power stations in the West has become expensive, but the reasons for that expense are not intrinsic to nuclear power. Part of the problem is that the previous generation of reactors lasted so long that, by the time they needed to be replaced, many of the people who had designed and built them had retired or died. Much of the practical knowledge gained from constructing those reactors had been lost.

In Europe, this has contributed to a disconnect between designers, engineers and builders. Designers may sit in an office and produce a reactor design that can generate electricity and meet all the relevant regulatory requirements. Other stakeholders will also have their own requirements. Over time, these requirements evolve and new elements are added to the design. The result can be a sprawling and complicated structure rather than a concise design that is easy to build.

The clearest example is the European Pressurised Reactor, or EPR, versions of which have been built or under construction at Hinkley Point C, Flamanville, Olkiluoto, Taishan and Sizewell C.

People often point to the EPR project at Hinkley Point C and say: “Nuclear energy is expensive. There is no learning curve, and it will remain expensive.” That criticism ignores why this particular reactor design became so expensive.

Why the EPR became so complicated – the Germans

During the EPR’s concept phase, German utilities wanted important safety systems to be maintained while the reactor remained at full power – this was before Germany phased out nuclear power. This contributed to the adoption of four independent safety trains. A safety train is a complete set of equipment capable of performing a safety function, including pumps, pipes and valves, together with the electrical supplies, controls and supporting systems needed to operate them..

The trains had to be physically separated so that a fire, flood or other local failure could not disable several simultaneously. Each was therefore housed in a separate safeguard building with its own equipment, cabling, ventilation and electrical supplies. This improved redundancy and allowed one train to be unavailable for maintenance, but significantly increased the size and complexity of the nuclear island.

Maintenance at full power required a “two-room” concept within the inner containment structure, dividing the reactor building into an inaccessible equipment compartment surrounding the primary circuit and an accessible service area. This allowed certain maintenance activities to be performed at power, reducing the work required during refuelling outages. However, it required additional internal shielding walls, controlled access routes, closures and complex ventilation arrangements.

Separate from this internal division, the EPR also employed a double-wall containment structure. A prestressed-concrete inner wall formed the pressure-retaining containment, while a reinforced-concrete outer wall protected the reactor against external hazards. The annular space between them had to be maintained below atmospheric pressure and ventilated so that leakage through the inner wall could be collected and filtered. This added further concrete, reinforcement, formwork and ventilation equipment.

The European Pressurised Reactor was therefore a flawed design from the start. It incorporated operating and safety requirements whose construction consequences were underestimated. Individually defensible decisions accumulated into a design that proved exceptionally difficult to deliver with Europe’s weakened nuclear supply chain. Its designers had overlooked a basic fact: complexity is easy to add on a computer, but difficult to build in real life.

People point to Hinkley Point C and say, in effect, “Gotcha! nuclear power is expensive.” but before Hinkley Point C had began construction, there were delays at EPR projects in Finland, France and China. It was a questionable decision to assume that the UK, the global hub of delays, cost overruns and regulatory requirements would not suffer similar problems.

France builds the EPR2; Britain builds the EPR

Many of the EPR’s problems have been addressed in the EPR2. The basic reactor design and an electrical output of approximately 1.67 GW have been retained, but the surrounding plant has been reorganised to make it easier to build.

The EPR2 uses three safety trains rather than four. Preventive maintenance on frontline safety systems will instead take place while the reactor is shut down.

The “two-room” concept has also been removed. This simplifies the arrangement of internal walls, radiation protection, access routes and ventilation systems within the reactor building.

Double containment has been replaced by a single prestressed-concrete containment structure with an internal steel liner. This eliminates the annular space between the containment walls and the ventilation equipment associated with it.

The Nuclear Auxiliary Building has also been removed. Its functions have been transferred to the Fuel Building and the Waste Treatment Building, with the latter shared between two reactors at sites built as twin units.

Plan views of the EPR, left, and the EPR2, right, with the EPR2 having fewer and more regularly arranged buildings around the reactor.

Figure 1. Comparison of the principal buildings in the EPR, left, and EPR2, right. The EPR2 has fewer structures and a more regular layout. The annulus and Nuclear Auxiliary Building have been removed, while the four safeguard buildings have been reduced to three. Source: Mykhaylo Gopych, “The EPR2: A Short Presentation”, 2024.

It is easy to see from the figure that the second structure is far simpler. The internal walls are more regular, the double-containment structure is gone and the overall design is more buildable.

The EPR2 therefore shows how nuclear construction costs may be reduced through design. Fewer structures, more regular layouts and less complicated systems mean less concrete formwork, reinforcement, cabling and ventilation equipment. This reduces both material requirements and the amount of work that must be carried out on site.

EDF also intends to use more standardised components, prefabrication and modular construction. Building the reactors as a series of twin units should allow the same designs, components and construction methods to be used repeatedly. The EPR2 is therefore not simply a modified reactor. It is an attempt to restore the connection between reactor design and practical construction.

France has chosen to simplify the reactor design through the EPR2, whereas Britain will attempt to capture the benefits of repetition by building two further UK EPRs at Sizewell. Switching to the EPR2 – a more buildable design – would clearly be the logical choice. But it would also require a new UK licensing process, new detailed engineering and changes to a supply chain that has recently gained experience of constructing the existing design. Sizewell C will therefore test whether replication can overcome enough of the original EPR’s complexity to make the design economical. China’s decision provides a warning. When the second phase of Taishan was approved in 2025, the authorities selected two domestic Hualong One reactors rather than further EPRs.

The cost lies in inefficiencies

The cost of recent Western nuclear projects does not prove that nuclear power is fundamentally expensive. It proves that those particular projects were expensive. To understand why, we must consider how they were designed, manufactured and built.

Large construction projects struggle to improve without a feedback loop. A reactor must be designed, built and then examined to find which parts caused delays or proved difficult to manufacture and install. Those lessons must then be used to simplify the next reactor. Reactor two at Hinkley Point is being built 20 – 30% faster than Unit 1, so the repetition benefit has been substantial.

In the West, we have a tendency to do stop-start construction. The UK, historically, has designed and built a reactor, set about constructing it in an extremely inefficient manner, found it expensive, stopped building them and allowed the workforce and supply chain to disperse. Years later, we begin again with another unfamiliar design. We build a reactor, discover that it is difficult and expensive, fail to build another, forget how to build it and then repeat the process.

The cost of building anything comes partly from its materials and partly from the work needed to turn those materials into a finished product. The material itself may be relatively cheap. Processing it, moving it, installing it, inspecting it and documenting the work can be expensive.

Suppose, for example, that a tonne of steel costs £1,000. Producing standard lengths of reinforcing bar in a factory is comparatively simple. The expensive part is the labour required to cut, bend, position and weld or tie thousands of pieces into reinforcement cages.

The same principle applies throughout a nuclear power station. A pipe, cable or valve may not be particularly expensive by itself. Its final cost also includes the engineering needed to specify it, the work required to manufacture and install it, the inspections needed to verify it and the documents required to show that it meets the design. Complexity increases all of these costs.

This is also where large savings are possible. A mature manufacturing process moves work away from labour-intensive assembly on site and towards repeatable production under controlled conditions.

Plastic injection moulding provides a simple illustration. Machining each plastic component by hand would be slow and expensive. A mould and injection-moulding machine require a large initial investment, but once that equipment is in place, it can produce thousands of identical parts quickly. As production continues, the cost of each part moves closer to the cost of its material.

A nuclear reactor cannot be manufactured as simply as a plastic component, but the same economic principle applies. Standardised parts, factory production, prefabricated modules and repeated construction reduce the amount of labour required for each unit. Workers become familiar with the design, manufacturers improve their tooling and mistakes found in one project can be removed from the next.

This does not mean that a reactor will ever cost only as much as its raw materials. It means that a mature construction programme can reduce the additional cost created by unfamiliar designs, inefficient working methods and excessive on-site labour.

The important question is therefore not merely how much the first reactor costs. It is whether the programme is organised to allow learning, so that the second reactor costs less to build and the third costs less again.

Repetition can make EPR construction faster, but it cannot remove the many of the constraints inherent in the design. This is one reason why the French revised it to create the EPR2.

This feedback loop, combined with a simpler design, is also one of the reasons why small modular reactors are appealing.

Why small modular reactors are appealing

In discussions about nuclear power, economies of scale are often treated as though they simply mean making each reactor larger. A larger reactor is then assumed to represent better value for money because it produces more electricity. People talk about economies of scale, but economies of scale come from building many copies of the same thing and getting good it it, not from building one massive thing.

Therefore, a programme that constructs a series of smaller reactors creates repeated opportunities to improve the design, manufacturing process and construction method. Small modular reactors, such as the Rolls-Royce SMR, may address many of the problems associated with recent large-reactor projects. We know that very large construction sites are difficult to manage, particularly in the UK, where nuclear projects face onerous safety, regulatory and documentation requirements. As a project grows, so does its workforce, the number of contractors and the burden of coordinating their work. More time is spent managing access, inductions, inspections, interfaces and safety procedures. On modern large building sites, a new worker might have to wait two weeks or more for a site induction, and cannot start work until then. A smaller reactor that requires less work on site, because more of it is manufactured in factories, makes it easier to identify where delays and mistakes occur, but can also avoid the challenges of managing extremely large sites.

Large projects also suffer from the human limitations of their workforce. A bigger team will usually experience more turnover during construction, meaning fewer people remain for the entire project. A worker may spend most of a career helping to build only one or two large reactors and have little opportunity to apply what was learned.

A programme of smaller reactors would allow teams and suppliers to repeat the same job more often. Problems found in one unit could be corrected in the next, while tools, factory processes and installation methods could be refined over time. Repetition is how people, organisations and industries become good at building things.

Smaller reactors should also take less time to build. This matters because a large part of the cost of a nuclear project comes from financing. Interest on loans accrues throughout construction, while the reactor is not yet operating or earning revenue. Delays increase the final cost even when the physical reactor itself does not change.

The UK government has attempted to address financing issues through the Regulated Asset Base model, but changing how a project is financed does not eliminate the costs that accumulate during construction.

A shorter construction programme reduces the period over which interest accrues and limits the financial consequences of delays. It also reduces the amount of capital at risk in any single project and allows investors to receive a return sooner. Lower risk can lead to lower interest rates and lower overall costs.

An SMR is not automatically cheap merely because it is small. It may have a higher construction cost per megawatt than a large reactor when considered as a single unit. Its advantage is that a programme of many smaller reactors creates repetition, makes better use of factories and specialised tooling, and allows improvements to be carried from one unit to the next.

Shorter construction times, lower financing risk and a faster feedback loop can reduce costs across the fleet. Instead of betting everything on a small number of enormous projects, an SMR programme can improve through repeated construction.

The extraordinarily high cost of recent Western nuclear projects is not an immutable characteristic of nuclear power. It reflects a combination of demanding reactor designs, immature projects, weakened supply chains, inefficient construction and expensive financing.

The EPR2 shows how a large reactor can be simplified by removing simplifying buildings, systems and operating requirements. Small modular reactors offer another route: smaller projects, greater factory production, shorter construction times and more opportunities to learn.

If we design reactors around how they will actually be built, maintain stable construction programmes and apply the lessons from each unit to the next, nuclear power will become cheaper.

Back to top ]]> Energy https://johnewbank.co.uk/why-nuclear-power-can-and-will-get-cheaper/ Sat, 22 Aug 2026 23:00:00 GMT Huel Review, Is It Worth It? + refer a friend code https://johnewbank.co.uk/huel-review/

Without the hype

If you are here for the discount, use my referral code: REF-JOHNE636 or you can use REF-VICKYB1464

At the time of writing, this gives new UK customers £20 off their first order of £60 or more.

I keep the current terms on my Huel referral code page. If one code doesn’t work, try the other.

Huel review: In short

Verdict: Yes, Huel is worth it in certain situations. If the alternative is skipping breakfast, eating a chocolate bar and crisps, or ordering a takeaway after work, a Huel bar or instant meal makes sense.

Rating: 4 out of 5 — convenient and filling, but relatively expensive compared with food prepared at home.

Best for: Busy mornings, late finishes, travelling, keeping in your gym bag, or providing an alternative to fast food. Huel is most worthwhile when it replaces an unhealthy or expensive convenience option. It saves money compared with a takeaway, but not compared with cooking a simple meal at home.

Watch out for: The flavours and textures vary considerably. Some are very good, while others are bland or claggy.

Why we bought Huel

I did not originally buy Huel for myself. My girlfriend was looking for a convenient way to eat more protein, so I suggested replacing some of her usual cereal bars with protein bars. Everyone knows that if you want the gains, you need to eat the protein. The problem is that consistently eating enough protein can be a bit of a faff.

After doing her own research, she decided to try Huel’s Complete Nutrition Bars and Hot & Savoury Pots. The bars are an easy snack, while the pots are something quick to eat if back late from work or after netball.

I know that Huel markets itself as ‘complete nutrition or meal replacement’ but I’m not convinced by that. Really it’s a shortcut for occasions when there is not enough time or energy to prepare proper food.

Huel Complete Nutrition Bars review

The Huel bars are very filling and convenient. They are easy to keep in your work bag, gym bag or car, and they require no preparation.

They taste reasonably good, although that is within reason. It isn’t like a gourmet meal.

Our favourite is Dark Chocolate Raspberry. The raspberry adds some sweetness and makes the bar more interesting.

The Peanut Caramel bar is also good. But the Chocolate Fudge Brownie is rather claggy and doesn’t have a very interesting taste.

Four Huel Complete Nutrition Bars in different flavours laid out on a table.

A selection of Huel Complete Nutrition Bars.

Huel Hot & Savoury Pots review

So I don’t eat these at all, so these are the views of my girlfriend.

She likes Hot & Savoury Pots. They only need boiling water, and cook fully just from that.

She prefers the Asian-inspired flavours. The Katsu Curry Noodles are particularly good, while the spicy Fiery Chick’n Noodles really are hot.

The non-Asian flavours have been more mixed. The Pasta Bolognese is perfectly fine, but the Spaghetti Carbonara can be rather gooey and claggy.

Buying a selection box makes sense for your first order because the flavours are quite different. Once you know what you like, you can buy boxes containing your preferred flavours instead.

She has prepared the pots in a food flask when going out, which is useful for travelling or working somewhere without a kitchen.

Huel Lite Ramen review

Her first impression of Huel Lite Ramen was much less positive. It was bland, and the noodles did not seem to cook as well as those in the regular pots. The spicy pots were not remotely spicy.

An orange Huel Lite Hot & Savoury pot on a table.

One of the Huel Lite Hot & Savoury pots.

Drawbacks and is it worth it?

The main drawback is cost.

At the time of writing, Huel lists its Complete Nutrition Bars from £2.29 per bar and Hot & Savoury Pots from £3.05 per pot, depending on the order and subscription option. That is cheaper than most takeaways, but considerably more expensive than making a simple meal or snack yourself. (uk.huel.com)

Texture is the other major drawback. Some Huel products can be dense, gooey or claggy, and the experience varies substantially between flavours.

So overall despite the cost, it is worth it if it replaces a takeaway, café lunch or collection of snacks bought on the go, it can save you money. You spend a few pounds on Huel rather than considerably more on convenience food.

What should you try first?

We would recommend:

  • A mixed box of Complete Nutrition Bars
  • A selection box of the regular Hot & Savoury Pots
  • Dark Chocolate Raspberry and Peanut Caramel bars
  • Katsu Curry Noodles if you want to choose one pot flavour

I would not order a large quantity of any flavour before trying it

Based on our experience, we would also choose the regular Hot & Savoury Pots over Huel Lite Ramen.

<p>Ad: Huel Review – Is It Worth It? + £20 Discount Code</p>

Back to top ]]> Reviews https://johnewbank.co.uk/huel-review/ Thu, 20 Aug 2026 23:00:00 GMT Does Passive Cooling Work? https://johnewbank.co.uk/does-passive-cooling-work/

Without the hype

Introduction

When it comes to overheating homes there seem to be two schools of thought. The first is that we should use passive cooling — preventing heat from getting in. The second is that air conditioning is better and needed.

Being somewhat of an experimentalist, I thought I would test the passive side and see what kind of results it can deliver in hot weather. Below is a description of my actions, and whether it was a success.

Firstly, the maisonette flat I am in overheats. It has a very low heat loss around 2kW and is well insulated. Once the heat is in it doesn’t naturally flow out. This isn’t due to a lack of ventilation — there are windows on both sides of the house, which allow for a through-draft, and also rooflights which can be opened to allow heat to rise up and out of the building. Nevertheless, natural ventilation is not sufficient to cool the building. I cannot stress how useless natural ventilation is at cooling this flat.

With that in mind, I will outline the steps I have taken to see how effective passive cooling can be.

What I Did

1. Ceiling Fans

Both upstairs bedrooms now have ceiling fans. These have been a huge success — I’ll go into more detail later, but just by having a quiet, large fan circulating air, it’s much more comfortable to exist in a hotter room. Even if the temperature doesn’t fall significantly, you’re still able to fall asleep.

A three-blade ceiling fan in a loft bedroom with sloping ceilings.

A ceiling fan keeps the air moving, which makes a hot room bearable.

The bedroom ceiling fan, with the windows behind covered in reflective radiator foil.

The fan, with foil on the windows behind.

2. Radiator Foil on the Upstairs South-Facing Windows

I iterated on this. I initially started using just sheets, then tried emergency blankets (which tore in the wind), and finally settled on radiator foil. This works; however, it is apparent that I’m fighting a losing battle against the heat. While I’m stopping the radiative heat getting in, it doesn’t stop the room getting hot, instead it reduces the sauna effect.

A dormer window covered on the inside with reflective radiator foil.

Radiator foil on an upstairs south-facing window.

Close-up of crinkled reflective foil fixed across the inside of a window.

The foil reflects radiant heat, but doesn’t stop the room warming.

The crinkled foil on the window from a slightly different angle.

The foil from another angle.

3. A Makeshift Awning Downstairs

This was more of an experiment than anything — trying to reduce the amount of heat that hits the bricks and gets absorbed. I can’t say how well it works, but it reduces solar gain to the balcony, so it does a little.

A white sheet hung from an upstairs dormer window down over the ground-floor patio doors as a makeshift awning.

A makeshift awning to keep the sun off the brickwork downstairs.

4. A Fan Blowing Air Out of the Rooflights

I noticed that with the rooflights open, there was still not a significant draw of air through the property. I realised that if I could blow air out of these rooflights, I could instead force convection in the property. This has worked to an extent — because we run the ceiling fans, there’s not so much stratification of heat across the room, so perhaps this isn’t quite as effective at pulling out the very hot air as it could be. But my goal is to overcome the lack of air flowing though the property and this helpscreates a draught. I’m tempted to get a bigger fan to do this, but in all honesty, I think it’s hit peak efficiency.

A fan on the landing pointed up at an open rooflight.

A fan blowing warm air out through the rooflights.

The Results So Far

Inside against outside temperature, 17 to 24 June 2026 (°C)

Inside against outside temperature over seven days (outside from Open-Meteo, dashed), with daily peaks and lows marked.

The graph above shows temperatures over the last seven days. The top line is the bedroom, followed by the home office and the lounge. As you can see, the upstairs gets hotter than downstairs, with the bedroom the hottest overall. This is because it is south-facing and has rooflights.

The dashed line is the outside temperature from Open-Meteo. It reads a bit below what we experience locally, but we don’t currently have an external temperature logger.

All of these readings are with each of the interventions I mentioned previously in place. Each day we keep all the windows closed until the outside temperature falls below the inside. At that point, we ramp up the ceiling fans and open the rooflights.

If you look at the daily low temperatures over time, what you see is that despite our efforts, more and more heat is being retained each day. We are unable to equalise the external and internal temperatures. As the external temperatures increase, so do the internal temperatures. On the night of the 23rd–24th, the minimum bedroom temperature was over 25°C — far above what is comfortable in still air.

Despite it being that hot, we were able to sleep reasonably well because of the ceiling fan. It provides a nice breeze and is quiet. In previous years, before we had temperature monitoring, this room was stifling without it.

Daily lows and highs, 17 to 24 June 2026 (°C)

Daily minimums and maximums both rose across the week. The 24th is the night before the readings ended at 9am, so its high is only the morning.

Daily lows and highs as a table
Low (°C) High (°C)
Day Bedroom Home office Lounge Outside Bedroom Home office Lounge Outside
Wed 17 Jun 20.4 22.4 22.1 16.9 26.1 25.7 26.3 23.8
Thu 18 Jun 21.6 20.9 21.7 16.7 26.1 26.5 25.7 24.2
Fri 19 Jun 22.6 21.4 23.6 16.0 29.1 28.4 27.8 28.5
Sat 20 Jun 20.6 22.1 23.6 17.3 26.3 26.7 26.4 24.1
Sun 21 Jun 21.7 22.4 22.2 17.1 29.4 29.5 27.9 29.6
Mon 22 Jun 21.6 20.6 22.6 17.9 29.1 28.1 26.4 27.7
Tue 23 Jun 23.1 21.2 23.5 18.6 30.8 29.7 28.2 33.1
Wed 24 Jun 25.3 25.0 26.1 21.2 29.0 28.1 27.8 26.8

Going back to the temperatures — at what point does the temperature increase stop? If we have sustained hot weather for weeks and the nights don’t cool down, it becomes immediately obvious that passive measures are not sufficient to cool the property. This is a risk going forwards: if we continue to have hotter summers, internal temperatures will be largely set by the daytime peaks as the building’s thermal mass and surrounding buildings, roads, etc. store more heat.

The minimum temperatures of the home office and the bedroom have risen by 5°C over the past week, from 20°C to over 25°C. This isn’t even the end of the heatwave.

Ceiling fans make the biggest difference.

Adding the ceiling fans has had the greatest effect and comfort, just having the air move over your skin to help sweat evaporation makes a very hot room livable in. If you are in an area that isn’t prone to significant overheating and you want to take the edge off I’d go with these as a first step.

Passive measures won’t be good enough for cooling, in a warmer UK

these experiments are a bit hacky and temporary But I believe they demonstrate that passive measures are not going to be suitable for many UK homes, especially those in the South or with overheating issues.

That isn’t to say that you shouldn’t do passive measures, more that the physically reality is that if a room gets too hot then the outside temperature must be cooler than the room for the room to cool. If there isn’t the temperature drop off, then you can’t cool. It’s as simple as that.

Back to top ]]> Heat pumps https://johnewbank.co.uk/does-passive-cooling-work/ Tue, 23 Jun 2026 23:00:00 GMT Robert Welch Radford Bright Cutlery Review + 15% Discount https://johnewbank.co.uk/robert-welch-cutlery-review-and-discount_code/

Without the hype

Radford Bright Cutlery Review: In short

Verdict: Yes, I’d recommend the Robert Welch Radford Bright cutlery. It is excellent cutlery: comfortable to hold, reassuringly weighty, and extremely robust. I even used one of the spoons as an ice cream scoop without bending it — rogue, I know — but it does show how strong it feels.

Rating: 4.5 out of 5 – half a point reduction as it is quite pricy.

Best for: People who want comfortable, strong cutlery that feels like it could last a lifetime.

Watch out for: Think carefully about which set you actually need. Do you really need two different sizes of knives and forks? We went with the larger size only and are very happy with that. Also consider how many people are in your house. For two people, I would recommend buying two sets of six as a minimum, otherwise you may still end up running out.

Biggest lesson: Do not wash stainless steel cutlery with aluminium in the dishwasher. Robert Welch warns on the packaging that aluminium can cause stainless steel to rust in the dishwasher.

Why we bought it

Boxes of Robert Welch Radford Bright cutlery on a worktop, one showing a place setting on the front.

The Radford Bright sets as they arrived.

My girlfriend had a cutlery problem. She had several different cutlery sets all merged together, but had always wanted a proper matching set of knives and forks. I found the mismatched cutlery mildly frustrating too, and we also regularly ran out of knives and forks because there were never quite enough.

I housesit so I am exposed to many different cutlery sets. My girlfriend often comes to visit, and we realised that the only cutlery set that stood out at us from all the sits was the Robert Welch Radford Bright 5mm set. We corroborated these thoughts, by heading to John Lewis.

John Lewis often has cutlery displays, at the Kingston Branch we explored all the Robert Welch that they had on display and decided that the Radford Bright was the only one that looked and sat right. It’s very elegant, has the right weight, and is timeless.

First impressions

Robert Welch Radford Bright cutlery unpacked from its boxes and bags on a worktop.

Unpacked, with a good weight and balance to every piece.

The Robert Welch Radford Bright cutlery is excellent. The pieces have a good weight and balance. A lot of cheaper cutlery feels slightly too light or flimsy, as though it might bend if you press down too hard. In my experience, some of it eventually does.

How they feel in the hand

This is probably the main reason we chose them.

The Radford Bright knives, forks, and spoons sit very well in the hand. They have a good heft to them providing a sturdy feel. The handles are smooth and comfortable, and the proportions feel right. Some sets I’ve come across feel too thin and have angular edges that dig into your hands.

How robust are they?

I used the table spoon as ice cream scoop to dig out some very solid ice cream. It survived without bending. That gave me quite a lot of confidence in the set.

You could no doubt bend them if you really tried, but they are significantly sturdier than most cheap cutlery I have used. They do not feel delicate or fragile. They feel like they are made to be used.

Will Robert Welch Radford last? Old versus new.

An older Robert Welch Radford table knife beside a new one, on a speckled worktop.

Old and new Radford table knives side by side.

An older Robert Welch Radford knife blade, showing the engraved logo, beside a new one, on a speckled worktop.

Old and new Radford knife blades side by side.

An older Robert Welch Radford fork and knife beside a new one, on a speckled worktop.

Old and new Radford forks and knives side by side.

An older Robert Welch Radford handle end beside a new one, on a speckled worktop.

Old and new Radford handle ends side by side.

An older Robert Welch Radford table fork beside a new one, on a speckled worktop.

Old and new Radford forks side by side.

An older Robert Welch Radford knife beside a new one, on a speckled worktop.

Old and new Radford knives side by side, from another angle.

An older Robert Welch Radford dessert spoon beside a new one, on a speckled worktop.

Old and new Radford dessert spoons side by side.

An older Robert Welch Radford serrated steak knife beside a new one, on a speckled worktop.

Old and new Radford steak knives side by side.

An older Robert Welch Radford spoon handle end beside a new one, on a speckled worktop.

Old and new Radford spoon handle ends side by side.

An older Robert Welch Radford teaspoon beside a new one, on a speckled worktop.

Old and new Radford teaspoons side by side.

An older Robert Welch Radford steak knife blade beside a new one, on a speckled worktop.

Old and new Radford steak knife blades side by side.

An older Robert Welch Radford set of fork tines beside a new one, on a speckled worktop.

Old and new Radford fork tines side by side.

An older Robert Welch Radford spoon bowl beside a new one, on a speckled worktop.

Old and new Radford spoon bowls side by side.

We had our cutlery delivered to one of the houses I was staying in, which also happened to have an older Robert Welch Radford set. That was quite helpful because it gave us a direct comparison between a new set and one that had clearly been used for years.

The Robert Welch I saw in my housesits was “decades old”. They have dulled slightly over the years, as they haven’t been polished, but other than that they look as good as new. The knives also seem to retain their cutting ability well over time.

It is quite easy to repolish stainless steel which reassures me that if we wished to keep ours shiny forever we could.

What we chose

We chose the Robert Welch Radford Bright 30 piece set with ‘free steak knives’ this gives six of each knives, forks, spoons, teaspoons, and steak knives. Most larger sets have both smaller knives and forks, which I don’t think are needed unless you regularly lay out formal place settings or host three-course meals. For everyday use, one uniform size makes more sense to me.

We also got some serving spoons, additional teaspoons and cheese knives (because everyone needs a cheese knife)

A boxed Robert Welch Radford serving set, with a large serving spoon and smaller pieces.

We also bought serving spoons, extra teaspoons and cheese knives.

What I think you should choose

I would suggest the 30-piece Robert Welch Radford Bright set, but you might want to buy two sets or more. We bought extra forks and spoons in addition to what was in the set, but it might be better just to buy another set of 30.

There is also a smaller 16-piece set with four of each main item, excluding the steak knives.

Dishwasher care

Robert Welch says aluminium can cause stainless steel to rust in the dishwasher, so avoid washing them together.

Downsides

Realistically the only downside is the price. Robert Welch cutlery is not cheap, which is why I have knocked half a point off the rating. But other than that, there isn’t really anything other than having to think carefully about what you need.

Robert Welch has many sets and variations some with small knives and forks you may not use, so it is worth checking what is included before buying.

Is it better than cheaper cutlery?

It does exactly the same job as cheap cutlery, it won’t make your food taste better. You are buying purely for the aesthetics, so that is up to you. The Robert Welch Radford Bright set feels like something you buy once and use for years. Whereas some cheaper sets seem like they will only last a few years.

Would I recommend the Robert Welch Radford Bright cutlery?

Yes, I would. It is comfortable, strong, nicely weighted, and elegant. After using lots of different cutlery sets while housesitting, this was the one that stood out.

For me, it is a 4.5 out of 5. The cutlery itself is excellent, but it is expensive enough that I cannot quite give it full marks.

A full set of Robert Welch Radford cutlery arranged in a wooden cutlery drawer.

The full set in the cutlery drawer.

Cheaper alternatives to Robert Welch?

Just before we bought the Robert Welch we were looking at the ProCook Berkeley cutlery set. It is a perfectly adequate set, just not as nice as the Robert Welch set.

Back to top ]]> Reviews https://johnewbank.co.uk/robert-welch-cutlery-review-and-discount_code/ Sat, 06 Jun 2026 23:00:00 GMT What uses more Electricity heating or Cooling? https://johnewbank.co.uk/what-uses-more-electricity-heating-or-cooling/

Without the hype

Updated October 2026 with data to 16 October 2026, which adds this summer’s cooling. The figures in the text are recalculated from it, the charts are now interactive, and outdoor temperatures now come from ERA5 weather data for the area rather than the sensor by the outdoor unit, which picks up the unit’s own exhaust air (see below).

It is often assumed that running an air-to-air unit in cooling mode uses more electricity than running it in heating mode. Here in the UK, most air-to-air heat pumps are installed primarily as “air conditioning”, and sized around the familiar 125 W/m² cooling rule: roughly 1,250 W of cooling capacity for every 10 m² of floor area, with adjustments for glazing, occupancy, etc.

But are cooling loads in the UK really higher than heating loads? Contrary to the prevailing narrative, my measurements suggest they are not, or at least, that it isn’t a simple case of directly comparing cooling to heating loads. Everything below comes from a single air-to-air heat pump I monitor in Surrey, the same unit used for winter heating and summer cooling.

Peak heating and cooling energy usage

The highest-use heating day drew 22.4 kWh of electricity; the highest-use cooling day drew 10.8 kWh.

Electricity used on the highest-use heating and cooling days (kWh)

The peak heating day used about 2.1 times the electricity of the peak cooling day. These are the two highest-electricity days in the record, not necessarily the coldest and hottest days.

The reason for this difference is relatively straightforward when you think about it. In winter, the outside temperature can sit well below the indoor target for the full 24 hours. So the potential heat loss from the structure over those 24 hours is very high, Summer cooling is different. The hottest part of the day may need active cooling, but UK nights are usually much closer to 21 degrees, with temperatures above 20 degrees being called ‘tropical nights’ and being somewhat uncommon.

Mean hourly electricity usage for heating and cooling

The chart below plots average electricity use by hour of day for the ten hottest and ten coldest days. Cooling clearly rolls on during the day and rolls off overnight, while heating use is much more constant.

Average electricity use by hour of day (kW)

Average electricity use by hour of day. Heating runs fairly steadily around the clock, while cooling switches on through the day and rolls off overnight as outdoor temperatures fall back toward the indoor target.

In the cooling season once the room is cool, any overnight heat flux back into it is much smaller, so the load drops away. But additionally, as the outside temperature is relatively close to the target temperature the aircon becomes more efficient, so it can extract more heat for a given unit of energy.

This is not a perfect like-for-like comparison. As the room being monitored is not normally occupied overnight in summer, so the homeowner often turns the unit off at night when cooling. However, in this climate, night-time temperatures often allow that once the room is cool, then it tends to stay cool.

Efficiency: COP for heating was lower than Cooling COP

The peak heating day was not just longer; it was also less efficient, according to my measurements, at least.

On 4 January 2026, the unit delivered 53.6 kWh of heat from 22.4 kWh of electricity, a COP of 2.39. On 26 June 2026, it delivered 46.4 kWh of cooling from 10.8 kWh of electricity, a COP of 4.31. Part of the drop in heating efficiency is down to a fault in the Mitsubishi MSZ-LN35VG2 defrost logic, which I won’t go into here.

Put another way, each kWh of heat delivered on the winter peak required 0.42 kWh of electricity, while each kWh of cooling on the summer peak required only 0.23 kWh.

The peak days: how much heat was moved, and how efficiently

The heating peak moved more heat (53.6 against 46.4 kWh) and did it less efficiently (COP 2.39 against 4.31). More work at a lower efficiency multiplies out to far more electricity.

The outdoor unit recirculates its own air

I think the summer efficiency could be improved further still. A temperature sensor on the intake of the external unit suggests it is recirculating a lot of its own exhaust air, which is surprising given that it is not enclosed and sits about a metre and a half above the ground. I think this has implications for air-con installers everywhere.

Recirculation on 2 July 2025: the sensor by the outdoor unit against the real air temperature

We can see in the above chart how the unit may be recirculating the exhaust air: the outside temperature measurement (near the unit intake) ramps up substantially when the unit turns on and falls when it is off, while the real air temperature doesn’t. On the 108 summer days with both cooling and daytime off periods, the sensor read a median 1.7 °C warmer, relative to the real air temperature, while cooling than while off, and more than 7 °C warmer on one day in ten. Sun on the sensor can add to this: on the day shown, the rise at about 15:00 came while the unit was still off, and the jump when it started at 18:00 is the recirculation. Because of all this, the temperatures in the rest of this post use ERA5 weather data for the area instead of that sensor.

Degree-hours: Another way to think about load

We can look at energy usage vs temperature another way, using by looking at number of hours where outside temperature deviates from 21°C multiplied by the number of hours it lasts. A 10 °C gap from 21 °C sustained for 12 hours is 120 degree-hours.

On that measure, the peak heating day had around 533 heating degree-hours, while the peak cooling day had around 198 cooling degree-hours. Heating had 2.7 times the degree-hours of cooling, yet used only about 2.1 times the electricity. Which indicates that cooling loads when compared to heating loads are higher, when we consider the temperature differences.

Daily electricity use against degree-hours from 21 °C

Electricity use against degree-hours from 21 °C. The large orange dots are the ten coldest days and the large blue dots the ten warmest. For each extra degree-hour of demand, cooling adds more electricity than heating.

In the above chart the big orange and the big blue dots have the lowest and highest mean temperatures respectively. We can see how cooling load increases with fewer degree hours from 21 than heating load.

It is important to note that degree-hours only count the gap in air temperature, but summer cooling load also has to fight solar gain through glazing and the latent load from humidity, neither of which shows up in outdoor air temperature. However, it does seem like a useful proxy for predicting load, as we know outside temperature in the UK summers strongly aligns with it being sunny.

I will be interested to see how this chart develops as more data accumulates.

Mean outdoor temperature vs electricity use

We can look at this another way. Here, I plot electricity use against mean daily temperature difference from 21 °C, During winter, when the average daily outside temperature is 0 °C, it would read -21°C on this chart, conversely during summer if the mean daily temperature was 25°C it would read as 4°C on the chart.

Remember what I said earlier about the nights being cooler so bringing the summer average temperature down.

Daily electricity use against mean outdoor temperature, relative to 21 °C

We can see that both heating and cooling appear to follow a parabola of sorts. There is quite a lot of electricity usage near 21 degrees, mean outside temp, which may be a combination of heating and cooling on the same day. I need to check up on that.

October 2026: 17 days in the record had both more than 0.5 kWh of heating and more than 0.5 kWh of cooling.

In this dataset, the heating side reaches about -22 °C, which is significantly below 21 °C reference point.

Conversely the cooling side only, reaches about 8 °C above it. So even though the hottest days feel extreme, they are not as far from the outdoor ‘ideal’ mean temperature as the coldest winter days.

Additionally, while there is very little to no heating load at 5 °C below 21 °C, there is a lot of cooling requirement at 5 °C above average.

Conclusion

For this system, in this house, cooling does not require a higher sustained electricity load, nor does it cost more than heating.

The highest-use heating day used 22.4 kWh of electricity, compared with 10.8 kWh for the highest-use cooling day. The heating day had a larger load, ran for longer, and operated at a lower COP.

That does not mean cooling is trivial. It means the common assumption that “air conditioning requires higher loads than heating” does not hold for this example, but that might change with more data points.

Back to top ]]> Heat pumps https://johnewbank.co.uk/what-uses-more-electricity-heating-or-cooling/ Thu, 28 May 2026 23:00:00 GMT It’s Time to Ban AirCon! https://johnewbank.co.uk/its-time-to-ban-aircon/

Without the hype

Illustration of a portable air conditioner with its exhaust hose out of a window and flames outside.

Single-hose portable air conditioners cool the room by heating everything else (an AI-generated illustration).

Every year, when it gets hot, I think the same thing: it is time to ban single-hose portable air conditioners. (Yes, I’m boring like that.)

This isn’t some crusade against air conditioning; quite the opposite. Cooling is great, and well-designed and implemented cooling will make people’s lives better and sell more heat pumps. The problem is that many of the portable air conditioners purchased are terrible.

A single-hose portable air conditioner has a heat pump. It has a compressor that makes some refrigerant very hot. It pulls in air from the room and blows it across the heat exchanger, and then blows that hot air out of a window through an exhaust hose. That process is absurdly illogical.

These units take some of the air from the room they are cooling and eject it, inducing negative pressure inside the room. So to equalise the pressure, air must be drawn into the room from elsewhere. Ultimately this must be from outside: the warm place…

So a single-hose portable air conditioner is doing something fundamentally absurd: it is trying to cool your room while actively sucking hot air back into the building.

This creates a hilarious inefficiency: the unit has to work extra hard to make up for the fact that it is drawing in warm air from outside.

There are portable aircon systems that don’t have this design flaw; they are just uncommon in the UK. The first type is dual-hose portable units, which have an intake and an exhaust. In this case the indoor and outdoor air streams are kept separate. Intake air from one hose is passed over the heat exchanger, then promptly ejected through the exhaust hose. So no negative pressure is created, and only the air in the room needs to be cooled.

A white portable air conditioner with two hoses at the back and a remote control.

A dual-hose portable unit, with one hose drawing outside air in and the other blowing it back out.

With a single-hose unit, you are exhausting cooled indoor air. With a dual-hose unit, you are using outdoor air as the heat-carrying medium.

And of course, a proper split air conditioner is better again. The hot side is outside, the cold side is inside, and there is no large hose pumping room air out of the building. There are now portable versions of these, such as the Midea Portasplit. I’ve no idea how good these are.

The Midea PortaSplit, a portable indoor unit connected by a short refrigerant line to a small outdoor unit, with its phone app.

Portable split units, such as the Midea PortaSplit, keep the hot side of the system outside.

As an anecdotal example of how inefficient the portable units are: in one house where I installed a proper 3.5 kW split air conditioner, it used around 800 W to maintain roughly 24°C across about three-quarters of the house when it was 35°C outside. In the same broad conditions, a portable single-hose unit was using around 800 W just to cool one bedroom. Obviously this isn’t a laboratory test, but I’m relatively confident in the efficiency penalty.

In a way they do need to be banned, as people have no concept of how inefficient they are, or “WHY” they are inefficient. It is only something you will think about when you become deeply involved in the cooling world.

Long term, if the UK is going to use electricity for cooling, we should use it well. We should not be filling homes with machines that dump cooled room air out of the window and drag hot air back in to replace it.

We do not need to ban air conditioning.

We need to stop pretending that the worst version of air conditioning is good enough.

Back to top ]]> Heat pumps Environment https://johnewbank.co.uk/its-time-to-ban-aircon/ Mon, 25 May 2026 23:00:00 GMT ProCook Professional Ice Cream Maker Review + 15% Discount https://johnewbank.co.uk/procook-professional-ice-cream-maker-review/

Without the hype

In short

Verdict: Yes, I’d recommend the ProCook Professional Ice Cream Maker, with a few caveats. It makes very good ice cream, is much more convenient than a freezer-bowl machine, and I think it is reasonable value compared with other compressor ice cream makers. That said, I am not a connoisseur of ice cream makers and I have not used compressor models from other brands. Some of the other ice cream makers have the paddle in built into the bowl, which makes cleaning more difficult, this top mounted paddle makes cleaning and getting out all the ice cream easy.

Rating: 4 out of 5.

Best for: People who want to make proper homemade ice cream without keeping a freezing bowl in the freezer.

Watch out for: The machine churns and chills the mixture, but it does not produce fully hardened, ice cream, it’s more soft scoop straight away. I measured the temperature and it was around -14 degrees, so it does get cold!. But really you still need to transfer the ice cream to the freezer for a few hours.

Biggest lesson: Homemade ice cream is not just about the machine. Sugar, fat, golden syrup, alcohol, and mix-ins all make a big difference to the final texture.

Why I bought it

The ProCook Professional Ice Cream Maker, a black compressor machine, on a kitchen worktop.

The ProCook Professional Ice Cream Maker.

I bought the ProCook Professional Ice Cream Maker after previously using a small ice cream maker with a freezable bowl. That style of machine works, but I found it annoying. The bowl takes up a lot of freezer space, needs to be frozen well in advance, and in my experience never cooled the mixture especially well.

There is also the faff of having to rush when making mixes, which takes some of the fun out of making ice cream. If the bowl is only just cold enough, or the mixture is not chilled enough, or you take too long getting everything ready, the whole process feels a bit more stressful than it should.

The ProCook machine has a built-in compressor, which means it freezes itself while it churns. That was the main appeal. I wanted something I could use without having to sacrifice a large chunk of freezer space every time I fancied making ice cream.

The other reason we bought it was simply that it sounded fun. Shop-bought ice cream also seems to have become increasingly disappointing. A lot of it is full of gums, syrups, vegetable oils, or simply is not quite the proper ice cream you imagine it to be.

Making it yourself means you know exactly what has gone into it. If you compare it with higher-end supermarket ice cream, it can also work out cheaper. Premium brands are now often sold in 500ml tubs costing around £6. For around £3, we can make roughly 1200ml of ice cream with this machine.

First impressions

First impressions were mostly positive. The main unit feels reasonably well made and has a decent weight to it, which is reassuring. It does not feel like a cheap novelty appliance, although it is still very much a domestic ice cream maker rather than some kind of commercial machine.

One slightly odd thing was that mine came with no instructions at all. It is not a complicated machine, so this was not a disaster, but it did mean there was a bit of guesswork involved at first.

The internal bowl appears to be aluminium, which makes sense. Aluminium is a very good conductor of heat, so it should transfer the cold from the compressor to the ice cream mixture more efficiently than stainless steel would. It does not feel luxurious, but it does seem practical.

The weakest-looking part is the mixing paddle. It is made from fairly thin plastic and does not feel especially premium. That said, I do not think it is likely to break easily in normal use, partly because the motor is not especially powerful.

When the mixture gets too thick, the machine seems to stop churning rather than forcing the paddle through it. In practice, that is probably a good thing. I would rather the motor cut out than the paddle snap. It is at that point when you decant the mixture into a bowl and put it in the freezer.

How well does it work?

The important thing to understand is that this machine churns and chills the ice cream mixture, but it does not turn it into fully hardened freezer-style ice cream straight away. When the churn finishes, the texture is closer to a very soft soft-serve. It is cold, and developing thickness, but it isn’t cold enough to maintain structure straight away. It will start melting very quickly.

I had assumed that because the machine had a built-in compressor, the ice cream would come out more or less ready to scoop. In reality, the compressor makes the process much more convenient than a freezer-bowl machine, but it does not remove the need for final freezing.

What I made with it

So far, we have used the ProCook ice cream maker for proper ice cream and frozen cocktails. Some attempts worked brilliantly straight away; others taught me a lot about what actually affects homemade ice cream texture.

Mint chocolate chip ice cream

The first ice cream we made was mint chocolate chip, and it was excellent. This was the point where the machine started to feel worth having. The texture after churning was thick, cold, and smooth, and after a few hours in the freezer it became proper scoopable ice cream.

The main lesson from this first batch was that recipes matter a lot. We followed an American recipe and it was incredibly sweet. That is not necessarily the machine’s fault — sugar plays an important role in ice cream because it helps keep it softer — but it did make me realise that I would need to adapt recipes rather than just follow them blindly.

This is one of the fun things about making ice cream yourself. You can control the ingredients, but that also means you need to learn what the ingredients are doing.

Bright green mint custard base simmering in a saucepan, stirred with a spoon
Step 1 — the mint custard base cooking gently on the hob until it thickens enough to coat the back of a spoon.
Mint custard base poured into a ProCook ice cream maker ready to churn
Step 2 — the chilled mint base goes into the ProCook ice cream maker and the churn cycle begins.

Mint choc chip ice cream churning in the machine's canister, seen from above.

Step 3 — near the end of the churn, with chocolate chips folded through.
Freshly churned mint choc chip ice cream with chocolate flecks in the canister
Step 4 — cycle ended, with chocolate chips folded through the mint ice cream.
Churned mint choc chip ice cream scraped from the canister into a metal bowl
Step 5 — scraping the finished mint choc chip ice cream out, ready to freeze firm.

A scoop of homemade mint choc chip ice cream in a waffle cone.

Step 6 — in a cone.

Frozen cocktails

We also tried using it for frozen cocktails, including frozen margaritas and daiquiris. This worked better than I expected.

The advantage over simply shaking a cocktail with ice is that you can control the amount of water much more precisely. With a normal shaken cocktail, dilution depends on how much ice you use, how long you shake it, and how cold everything is. With the ice cream maker, you can decide exactly how much water goes into the recipe, then let the machine chill and churn it.

The results were good. I am not sure I enjoy frozen cocktails more than normal cocktails, but they are fun and I will definitely make more of them. It also makes the machine feel a bit more versatile than just being an ice cream maker.

A frozen blueberry daiquiri churning in the machine.

Peanut butter and Reese’s ice cream

The peanut butter ice cream was the most interesting experiment, because it went wrong before it went right.

Thick, pale peanut butter ice cream clinging to the paddle after churning.

The consistency of the ice cream straight after churning.
A cone of homemade peanut butter ice cream with Reese's Pieces, held up in a garden.
After the remix the peanut butter ice cream was excellent.

I made a peanut butter ice cream and added lots of chunky Reese’s Pieces towards the end of the churn. The problem was that I had not used any golden syrup or alcohol in the original mix, so the ice cream became very thick before it had reached the texture I wanted.

Once the Reese’s Pieces went in, they added too much resistance and the paddle stopped turning.

After transferring it to the freezer, the ice cream came out very hard. It was not icy or full of crystals, just too solid. I think this was partly because peanut butter is very fatty, which changes the consistency, and partly because the recipe did not have enough ingredients to keep it soft.

To rescue it, I let it soften, then re-churned it with a shot of rum and around 65ml of golden syrup. After that, it was excellent.

This was probably the batch that taught me the most. The machine can churn and freeze the mixture, but it cannot fix a recipe that is badly balanced. If the mixture gets too thick, especially with chunky mix-ins, the paddle can stop. That is not necessarily a fault, but it is something to be aware of.

What I learned about making ice cream

The main thing I have learned is that homemade ice cream is not just about freezing cream and sugar. The machine matters, but the recipe matters just as much.

Sugar is not only there for sweetness. It also affects texture. The more sugar there is, the softer the ice cream tends to be. This partly explains why some recipes, especially American ones, can taste extremely sweet: they are trying to get a soft, scoopable texture as well as flavour.

One useful trick is replacing some of the sugar with golden syrup. In the UK, golden syrup is an easy way to add invert sugar, which helps make ice cream smoother and less rock-solid after freezing.

Alcohol has a similar softening effect because it lowers the freezing point. You do not need much. A small amount of rum, vodka, Cointreau, or another suitable spirit can help stop homemade ice cream becoming too hard. Obviously this depends on the flavour you are making.

Fat also matters. The peanut butter ice cream showed this clearly. It did not come out icy, but it did come out very firm. That made me realise that “hard” ice cream and “icy” ice cream are not the same problem.

Mix-ins also need a bit of care. Adding chocolate chips, sweets, biscuits, or chunky pieces towards the end of the churn is usually sensible, but if the ice cream is already very thick, large mix-ins can add too much resistance and stop the paddle.

Downsides

The biggest downside is that the ProCook Professional Ice Cream Maker does not produce fully hardened ice cream straight from the machine. It gets the mixture cold and thick, but you still need to transfer it to the freezer if you want proper scoopable ice cream.

The second downside is the paddle. It feels a bit flimsy compared with the rest of the machine. I do not currently think it is likely to break, because the motor seems to cut out before too much force builds up, but it is the part I would be least surprised to have trouble with in the future.

The lack of instructions was also annoying. The machine is simple enough to use, but for a product like this I would have expected at least some guidance on timings, maximum quantities, and what to do if the paddle stops.

Finally, there is a learning curve. This is not really a fault of the ProCook machine specifically, but it is worth knowing. If you want good homemade ice cream, you need to think about sugar, fat, alcohol, golden syrup, and mix-ins. The machine makes the process easier, but it does not remove the need to understand the basics.

Is it better than a freezer-bowl ice cream maker?

For me, yes. Absolutely.

The freezer-bowl style of ice cream maker is cheaper and can work, but I found it annoying enough that I did not really want to use it. Having to store the bowl in the freezer is inconvenient, and if the bowl is not properly frozen, or your mix is not cold enough, the results can be disappointing.

The ProCook machine is much more convenient. You can decide to make ice cream without planning a day in advance around whether a large bowl is taking up space in the freezer. That alone makes the machine much more usable.

It still does not make instant fully frozen ice cream, but it removes the most annoying part of the cheaper machines.

Would I recommend the ProCook Professional Ice Cream Maker?

Yes, I would recommend it, with caveats.

It seems well enough made, it is much more convenient than a freezer-bowl machine, and it has already made some excellent ice cream. The mint chocolate chip was genuinely delicious, the frozen cocktails were fun, and even the peanut butter ice cream experiment turned into something excellent once I understood what had gone wrong.

The main thing to know is that this is not a magic box where you pour in ingredients and automatically get perfect ice cream. You still need to understand the basics of homemade ice cream: sweetness, softness, fat, freezing point, and when to add mix-ins.

The paddle also feels like the weak point, and I would have preferred clearer instructions in the box.

But overall, I am pleased with it. It has made ice cream making much more convenient, and it has also made the process more enjoyable. If you like the idea of making proper ice cream at home, and you do not want to deal with a freezing bowl taking up half your freezer, I think the ProCook Professional Ice Cream Maker is worth considering.

For me, it is a 4 out of 5 it does the job it is made to do. But I have concerns the paddle may not last years.

Back to top ]]> Reviews https://johnewbank.co.uk/procook-professional-ice-cream-maker-review/ Mon, 25 May 2026 23:00:00 GMT A2A Heat Pump Compressor Modulation: Why Size Doesn’t Tell the Whole Story https://johnewbank.co.uk/a2a-heat-pump-compressor-modulation/

Without the hype

Updated October 2026: charts 1 and 2 are now interactive and drawn straight from Daniel’s meter logs (zoom or pan to see the rest of each test), chart 3 now comes from my own unit’s monitoring with a look back over the whole record, and there is a new section comparing all six of Daniel’s units over the longer logs.

I was recently sent some very interesting real-world A2A (air-to-air) monitoring measurements from Daniel Lugosi. He has electricity monitors on a number of different heat pump brands, with his results corroborating something that John Cantor and I had already noticed: there are substantial differences in how units operate across different manufacturers.

With heat pumps, the headline capacity figure only tells you part of the story. I know there have been some recent articles arguing that customers shouldn’t have to think about compressors, and that these things don’t really matter. However, I think this is something installers will need to consider when installing for heating rather than cooling. People have higher standards for heating than for cooling, primarily because an aircon is expected to make some fan noise, but heating systems like radiators are silent — so people are far less tolerant of noise from a heating unit.

A 2.5 kW unit, a 4 kW unit and a 5 kW A2A unit might look easy to compare on paper. You would assume the smaller unit can run lower, the larger unit can run higher, and that everything scales neatly in between. In reality, it doesn’t work like that. It is very dependent on what is inside the heat pump — specifically the compressor and how that compressor is controlled.

Why I Think Minimum Modulation Matters

A heat pump does not simply turn electricity into heat at a fixed rate. A good inverter-driven unit should be able to vary its output depending on the heat demand. Pretty much all A2A units are inverter driven. All that means is that the speed of the compressor isn’t fixed — it can run at a range of speeds, maybe 40% up to 100%.

In mild weather, or in well-insulated rooms, the minimum modulation will dictate how little heat the unit can put into the room before it has to start cycling on and off. This is something manufacturers rarely make obvious in brochures, but I suspect it will make a considerable difference to comfort, noise, efficiency and probably long-term wear.

In cold weather, this is easy enough to understand. The house needs a lot of heat, so the heat pump runs harder. The room might need 1000 W of heat to stay warm at minus 5 outside.

But in milder weather, the room might only need 300 W to stay warm. If the heat pump can only deliver a minimum of 800 W of heat, then it will have to turn on and off a lot (cycling).

That is not necessarily disastrous. Pretty much all A2W units will cycle on warmer days. An air-to-water heat pump usually has water volume, pipework, radiators or underfloor heating which can buffer the heat. Air does not provide the same thermal buffer. If an air-to-air unit is oversized or has a high minimum output, the room can be heated very quickly and the unit must then turn off. It will then have to wait for the room temperature to drop again before switching on. When something is constant, you tend to filter it out; it is when something turns on and off that you notice it. This is especially relevant for air-to-air heat pumps because they heat the room directly.

So I believe the ability to run low and steady is valuable.

What the Measurements Show

Daniel’s first chart compares three smaller units:

  • Daikin FTXM25A
  • Mitsubishi AP25
  • Midea Mission II
Show

Chart 1: electrical input, three 2.5 kW units, 14 March 2026 (W, highest reading each minute)

Chart 1: Measured electrical input of three smaller air-to-air heat pumps during low-load heating. The Daikin FTXM25A is able to run steadily at a much lower input than the Mitsubishi AP25, while the Midea Mission II shows more pulsed behaviour. Use the buttons, or drag, to see the full 29 hours of the test.

The Daikin appears able to modulate down to roughly 125 W electrical input and sit there steadily.

The Mitsubishi AP25 seems to bottom out higher, around 260–270 W. That is still not excessive, but it is roughly double the Daikin’s lowest observed input.

The Midea Mission II behaves differently again. It shows much more pronounced pulsing, at times starting around 700–800 W, then dropping lower, then repeating. Later in the chart it behaves a little more like the Mitsubishi, but overall it looks less smooth.

That does not automatically mean the Midea is bad. Control logic can be complicated. Outdoor temperature, indoor temperature, fan speed, coil temperature and refrigerant control can all affect behaviour. But from this graph alone, both the Midea and the Mitsubishi AP25 are less refined at low load than the Daikin.

The second chart is perhaps even more interesting. It compares larger units:

  • Mitsubishi AP42
  • Daikin FTXTM40
Show

Chart 2: electrical input, larger units, 20 April 2026 (W, highest reading each minute)

Chart 2: The same measurement for the larger units, opening on 10:00 to 13:00 on 20 April. Use the buttons, or drag, to see the whole 37-day log, to 27 May. Times on both charts are UK time; the original version of this chart was labelled in UTC, an hour behind.

You might expect the larger machines to have a much higher minimum input. But both the Mitsubishi AP42 and the Daikin FTXTM40 appear able to run down at around 150 W. A smaller Hitachi Dodai 1.8 reportedly has a minimum input closer to 350 W.

What I want to get across is that a smaller, “more appropriately sized” A2A heat pump does not automatically mean better low-load modulation and comfort.

The unit I monitor the Mitsubishi LN35VG2 can modulate as low as 90W in some circumstances. Although, this in itself is oddly variable. It went through a period where it didn’t seem to modulate below 150W, I cannot figure out why this was the case.

Chart 3: my Mitsubishi LN35VG2 heating, 7 October 2025 (10-second data)

Chart 3: heating on 7 October 2025: a steady 105 W of electrical input for nearly seven hours, giving about 495 W of heat (a COP of 4.7), with 11 °C outside.

The same unit cooling, 3 August 2026 (10-second data)

Cooling on 3 August 2026: a steady 58 W of electrical input overnight, removing about 951 W of heat from the room (an efficiency of 17), with the air leaving the unit at about 12 °C against a room at 22 °C. That efficiency looks extraordinary, but it was a mild night with 22 °C outside, so there was very little temperature difference to pump against: the theoretical (Carnot) limit from the coil temperatures was about 25, and the unit managed 68% of it, about the same share as it achieves when heating. In cooling it runs at well under its lowest heating input.

My LN35VG2 over the whole record: how low it ran each day, heating and cooling

Added October 2026. Unlike Daniel’s meters, my monitoring includes the air temperature going into and coming out of the indoor unit, so heating and cooling can be told apart: when heating, the air leaving the unit is warmer than the room air going in, and when cooling it’s colder. Short cold spells of 15 minutes or less in winter are defrosts and are left out, as is some cooling I switched on by accident in February 2026. The chart above shows, for every day, the lowest steady input in each mode: the lowest median over 15 minutes of continuous running.

  • Heating: in every month with real heating use, the lowest steady input was between 78 and 100 W.
  • Cooling: month by month, in months with at least 20 hours of cooling: May 2025 55 W; June 2025 96 W; July 2025 67 W; August 2025 304 W; May 2026 228 W; June 2026 49 W; July 2026 45 W; August 2026 51 W. In summer 2026 it held a steady 45 to 51 W, roughly half its lowest heating input.

The spells when it wouldn’t go much below 150 W in heating show up in December 2025 and March 2026 (shaded). It isn’t simply colder weather: on days with a similar outdoor temperature (6 to 9 °C), its lowest steady heating input was typically 96 W in January and February 2026, but 139 W in March. I still don’t know why.

More data from Daniel

Added October 2026. Daniel has since sent longer logs: 37 days (20 April to 27 May 2026) for the three larger units, alongside the 29-hour March test of the 2.5 kW units. To compare all six on the same footing, the chart below uses each unit’s average power in every minute, from the meter’s energy reading, and asks two questions:

  • How low can it run without stopping? The lowest median power over any 15 minutes in which the compressor never switched off.
  • How does it usually run? The median power across every minute it was running.

A unit counts as running above 40 W; on standby they draw between 1 and 14 W.

How low each unit runs: lowest steady 15 minutes and typical running power (W)

The numbers
Unit Logged Hours running Lowest steady W Typical W Standby W
Daikin FTXM25A 29 hours 26 120 143 10.1
Daikin FTXTM40 37 days, used on 23 255 130 160 1.6
Mitsubishi AP42 37 days, used on 19 117 73 175 0.6
Mitsubishi AP25 29 hours 22 264 282 11.4
Midea Mission II 29 hours 16 298 304 13.9
Hitachi Dodai 1.8 37 days, used on 8 26 265 428 1.1

Standby power

When they weren’t running, the three units in the March test drew 10 to 14 W, while the three larger units drew 0.6 to 1.6 W. That sounds trivial, but a unit left on standby all year at 10 W uses about 88 kWh, which is roughly £22 at 25p/kWh.

Some of the difference may be the season rather than the model. Many outdoor units keep their compressor warm while idle in cold weather, and the March test was colder. The Mitsubishi AP42 hints at this: it drew about 12 W on standby on 20 April, the first day of its log, and under 1 W after that.

Things to bear in mind

Daniel’s logs record power only, not the mode, the room or the weather, so a few periods stand out as probably not normal heating:

  • Mitsubishi AP42, 25 to 27 May: it ran steadily at 73 to 95 W, about half its usual minimum. Before then its lowest steady run each day was 151 to 190 W, as in chart 2. The other two units were off all that week, so it may well have been cooling rather than heating; my own unit ran at roughly half its heating minimum when cooling in summer 2026 (see above).
  • Daikin FTXTM40, 20 May: its lowest steady run that day was about 310 W, against about 146 W on the other days it ran. That day it may also not have been in normal heating mode.
  • Hitachi Dodai 1.8: it ran on only 8 of the 37 days, about 26 hours in all, so its figures rest on much less data than the other two larger units.
  • Different conditions: the 2.5 kW units were tested over 29 hours in March and the larger units over five weeks of mostly mild spring weather, with long spells off (the Daikin FTXTM40 from 5 to 12 May and after 20 May; the AP42 from 2 to 12 May).

Panasonic Etherea Issues

While conducting research for my air-to-air report, I was contacted by an owner of Panasonic Etherea units, Panasonic’s premium consumer range. He was able to provide me with a significant amount of data showing how the unit was running, and how the room temperature was responding.

Power input chart showing a Panasonic Etherea air-to-air heat pump cycling on and off during heating, with power draw rising to around 400 watts before dropping back to zero instead of maintaining a steady low-power output.
Chart 4: Example of cycling behaviour on a Panasonic Etherea unit in heating mode. Although the long-term average input may appear low, the unit is not necessarily sustaining that input continuously.

One thing we noticed was that despite being a premium unit, the Etherea appeared poor at modulating. It would cycle on and off, drawing roughly 400 W when on and 0 W when off. If you take the long-term average of these cycles, the figure comes to around 190 W, which is more-or-less what the databook quotes for the unit’s minimum input. However, there is a meaningful difference between 190 W delivered continuously and 400 W delivered in on/off bursts.

This raises an uncomfortable question: how is the quoted minimum input actually being measured? it appears that the minimum input is time-averaged result of this cycling, rather than a true sustained low-power output. A separate source spoke to an Ebac air-to-water rep at a trade show, who confirmed that their minimum quoted figure included cycling. If that practice is widespread, the published minimum-input specs are not useful.

The Etherea seemed to have other issues too. The temperature sensor sits less than an inch above the condenser coils. In heating mode, hot air rises and corrupts that sensor’s reading almost immediately, so the unit “thinks” the room is up to temperature long before it actually is, and shuts off. On cooling mode the same unit behaves completely differently: cool air falls, so the sensor reads something close to actual room temperature, and the unit holds a steady, well-modulated power draw with no cycling. Some owners don’t seem to have this issue, but I have heard from a number that do.

The cycling problem is also worse at low fan speeds, because the hot air isn’t forced away from the sensor quickly enough. Running the fan harder helps, but the higher fan speeds measure above 50 dB at the unit, which is audibly far too loud for domestic heating. So the user is stuck choosing between accurate temperature measurement and acceptable noise.

The unit’s control logic doesn’t help either. In heating mode, the compressor turns off when the intake-air temperature sensor exceeds the internal setpoint by more than 2°C for three minutes, and turns back on after another three-minute wait, on when intake-air temperature falls. There is no PID control, instead it is a hysteresis threshold with a built-in 2°C overshoot.

Panasonic does not provide an official method for using a wall-mounted thermometer with these units, so the homeowner essentially had to build his own Home Assistant control system. This sets an artificially high target internal temperature — so the unit’s own sensor never reaches it — and switches the unit on and off based on a thermostat elsewhere in the room. This works, but it gives up what modulating ability the unit has.

The manufacturer has been unreceptive in assisting with this issue, unfortunately. And it isn’t a one-off: I have since spoken to another Etherea owner with the same problem, and I have heard of similar (though less severe) behaviour on Toshiba Haori units. Owners are typically left to work around the issue themselves, often by running the units at constant high setpoints to defeat the internal logic. You can adjust the ‘temperature offset’ in many of these units, which can help in some cases, but in others it causes the room to overheat. Which defeats the purpose.

The Missing Specification

What I would really like to see is a better database of real-world minimum modulation behaviour.

Not just:

This is a 2.5 kW unit.

But:

This unit can run continuously at around 120–150 W electrical input under mild heating conditions — without cycling.

That would be genuinely useful information for sizing and selection.

At the moment, this kind of knowledge mostly comes from enthusiasts measuring their own systems. That is why Daniel’s data is so interesting.

It also shows why brand and model range matter. A cheap small unit may not have the same modulation ability as a more expensive larger one. A cold-climate unit may have a surprisingly wide operating range. The compressor and controls matter at least as much as the nominal capacity. and in the worst cases, as with the Panasonic Etherea and the ElectriQ unit that John Cantor has written about, the temperature-sensing hardware matters too.

Bigger Is Not Always Worse…

With A2W heat pumps, it is typically best not to significantly oversize, as it increases costs and sometimes reduces efficiency and comfort. With A2A split systems (not multi-splits no data on these yet), it appears that in some cases (for some manufacturers) it may be advisable to “size up” to get a unit that can modulate better. Assuming you can pick the right unit.

That is slightly annoying, because it means you cannot just look at the capacity number and make a decision. You need to know something about the compressor, the control strategy and the minimum stable output.

Unfortunately, that information is often difficult to find. Manufacturers will usually publish rated heating capacity, maximum heating capacity, COP, SEER, SCOP, sound pressure, pipe lengths and operating temperature ranges. But the real-world minimum stable input is not always clear. Where minimum heating capacity is listed, it may not tell the full story. Two units may both claim a low minimum heating output and behave very differently in practice — and as discussed above, the quoted figure may well include cycling.

Back to top ]]> Heat pumps https://johnewbank.co.uk/a2a-heat-pump-compressor-modulation/ Mon, 18 May 2026 23:00:00 GMT Should You Get a Ceiling Fan (in the UK) https://johnewbank.co.uk/ceiling_fans_in_the_uk/

Without the hype

Are ceiling fans actually worth it in the UK? Logically they make sense, but should more people install them? Here are my early thoughts on the Philips Olas: what works, what doesn’t, what it cost, and the installation mistakes to avoid.

The short answer is unequivocally yes. In the recent heat wave our bedroom has hit over 30 degrees C. In the past we would not be able to sleep at all well, with the fan I’ve been able to sleep comfortably.

Why I Wanted a Ceiling Fan

I sleep in a south-facing room with a sash window and a Velux. It’s well insulated, which is great in winter, but in summer it turns into something approaching a sauna. Both windows wide open, a fan placed in the gap, air cascading in, yet the room stubbornly stays hot and I stay uncomfortable.

Standard pedestal or tower fans are limited. You have a choice: the air either oscillates back and forth, flapping at you, or it moves in a narrow cone at you along with the noise.

I’ve housesat across the country, across Europe in fact, and experienced all ranges of fans (quite the claim to fame). From fancy Dysons (which are noisy and a bit rubbish) to industrial cage fans (better but loud). All have the same problem: the air is moving rapidly in a narrow stream.

My foray into ceiling fans began as a thought about heating, not cooling. If someone was to try and heat their house with a single aircon unit, how would they push the air downstairs or upstairs? You can install vents, but they’re expensive and disruptive. You could put a small fan at the top of the stairs and try to circulate air, but that would get tedious quickly. So I thought, why not have a ceiling fan that can push massive volumes of air easily and quietly, while being cheap to run and install? That idea still lingers, but since I don’t have an aircon yet, I thought I’d start with a fan.

It’s strange that ceiling fans aren’t more common in the UK. When travelling abroad, staying in hotel rooms across Southeast Asia, the rooms all had one thing in common: a ceiling fan. They’re standard in countries where the heat is known to be stifling. Yet in the UK they’re rare. I think part of it is that our old building stock was poorly insulated and didn’t overheat like modern well-insulated houses do. Possibly it’s aesthetic. Ceiling fans have historically looked terrible, the kind of thing you’d find in a fading hotel bar. Dusty blades swirling around dimly lit, floral glass shades with only two of three bulbs working. Possibly British summers just weren’t historically hot enough. Possibly people just don’t think about them.

For now the air conditioning is waiting. The room clearly needs it. But the ceiling fan felt like an experiment worth trying in the meantime: cheaper, simpler to install, and if it didn’t work I wouldn’t have lost much.

How a Ceiling Fan Actually Cools You Down

Everyone knows a fan makes you feel cooler. On a hot day still air around you warms up, it saturates with moisture, and you stop losing heat. If the air moves, then there is evaporation of your sweat and you cool. You notice this on roasting hot days — it’s when you stop walking that sweat starts to bead.

A tower fan or a desk fan moves a small amount of air fast. A ceiling fan moves more air slower. The latter is more comfortable.

Which Ceiling Fan I Chose: The Philips Olas / CJOY 42 inch

I looked at a fair few. Most ceiling fans, I have to say, are ugly. There’s a kind of institutional dreariness to them. There are a few brands now making nicer-looking fans: Philips, Lucande, Ollyri.

I settled on a Philips Olas, which is the identical model to the CJOY 42 inch.

Philips Olas 42-inch ceiling fan on Amazon

Philips Olas 52-inch ceiling fan on Amazon

Philips Olas Black mount wooden blades

Cjoy 42-inch ceiling fan on Amazon (cheaper better instructions)

Newday 46-inch – looks similar but different (same controller)

Newday 46-inch – similar but different.

Philips Civx – thinner blades different design same remote

Philips Olas 42-inch white ceiling fan with three wood-effect blades and an integrated LED light, shown with its remote and box.

The Philips Olas 42-inch, which cost me about £120.

It wasn’t expensive. I paid around £120. Not a lot more than a standing tower fan. The blades are wood-effect plastic, which sounds cheap but turns out to be fine in practice. I don’t look at them enough to notice.

It was on sale, and I think it looks reasonably nice. It’s a 42-inch fan with three blades in white, and it’s got a built-in LED light.

It’s not a beautiful object, but it’s not unattractive either. It doesn’t draw attention to itself. That’s about as much as you can ask from a ceiling fan.

Philips Olas ceiling fan installed on a white bedroom ceiling, with a window behind.

Installed in the bedroom. It doesn’t draw attention to itself.

The Built-In Light

The light was a factor. I wanted something that could replace the existing ceiling fitting. It’s dimmable via the remote, and you can shift the colour temperature from warm white to daylight.

Warm white is the setting I use most. The diffuser helps. It’s a frosted plastic cover that throws light evenly. You wouldn’t want to use it without the diffuser as it has many small LEDs, rather than a bulb.

Philips Olas ceiling fan light switched on, its LEDs behind a frosted plastic diffuser.

The built-in LED light behind its frosted diffuser.

Switching between temperatures is done with the remote. One button cycles through warm, cool, and daylight. Simple, no apps.

The dimming works well enough, though it doesn’t go quite as low as I’d like. At its lowest it’s still bright enough to read by. You can’t use it for that very low ambient glow some people like in the evening. It’s a minor thing.

The remote is relatively large. If you change a setting on the remote then turn the light off at the wall, it remembers the setting you changed. So if you had the fan on and light off, then turned it off at the wall, then turning it back on at the wall would only turn on the fan. You’d have to find the remote to turn the light back on.

Philips Olas ceiling fan remote control held up below the fan, showing the speed and light buttons.

The remote, which also cycles the light between warm, cool and daylight.

How to Install a Ceiling Fan (and Mistakes to Avoid)

It is important to remember that the fan can’t just be screwed into a plasterboard ceiling. It ideally needs a joist or at the very least a wooden board to spread the load. Certain plasterboard fixings may be suitable but most are not. Some testing has been done here if you are unsure.

The installation wasn’t difficult, but it was a faff. The instructions are the main problem. They’re non-sequential in places, and some of the diagrams are genuinely bizarre.

Part of the issue is that some components come preassembled for packaging. You have to take them apart before you can build them back up in the correct order. I can see the logic — the box is smaller — but it adds confusion that could be avoided with better instructions.

The key mistake I made, and the one I’d tell anyone else to avoid, is where to position the mounting bracket relative to the electrical supply. My instinct was to centre it over the cable coming out of the ceiling. This is wrong. There’s a control box that slides into the mount, and if you’re centred on the supply there isn’t room for it. You either need to offset the mount, or cut a small channel in the plasterboard to run the cables through. I ended up doing the latter, which wasn’t the end of the world, but it was irritating.

The screws they supply are worth a mention. I sheared the head clean off one using an impact driver. That shouldn’t happen with a screw going into a ceiling joist. I swapped them out for better ones.

A final irritation: the instructions tell you to assemble the fan then fit the cowling over the mounting. Unfortunately, once you’ve assembled it all, it’s very difficult to unscrew the screws on the mounting that the cowling secures to. Loosen these screws before putting the fan on.

Despite all of this, once it’s up, it’s up. The whole thing took a bit over an hour, including the plasterboard surgery.

Does a Ceiling Fan Actually Help in a UK Bedroom?

Yes. More than I expected.

Before the fan my strategy was simple: open both windows and hope. The air would come in and out, but it didn’t really circulate. It sort of wafted. The walls, the furniture, the floor held their heat, and the room stayed stuffy well into the night.

With the ceiling fan running I can open the windows, ramp the speed up, and the air actually moves through the room. When I come back later the ambient temperature is noticeably lower. Not because the fan cools the air (it doesn’t), but because moving air strips heat from surfaces faster than still air ever can. The walls cool. The room cools. It’s the difference between letting something air dry and pointing a fan at it.

For sleeping, I run it on a low speed and it’s enough. The air moving across the room stops that stagnant feeling you get on hot nights.

There’s also a winter mode, which reverses the direction so it pulls air up rather than pushing it down. The idea is you run it on low and it circulates warm air that’s gathered at the ceiling back down into the room. I haven’t used this in earnest yet, but the logic seems sound.

As of writing this we have had the mega hot days in June, it has been fantastic, we ended up buying a second for the office. I would highly recommend a ceiling fan if you don’t have AC. But also maybe even if you do have AC and want to reduce the load.

How Noisy Is It?

This was one of the main reasons for getting a ceiling fan. I’m noise sensitive. I sleep with foam earplugs. My tower fan, which is marketed as whisper-quiet, produces a low hum on its lowest setting that cuts straight through the earplugs and annoys me. Not loud, just present.

On the ceiling fan’s lowest setting (which is a bit too fast) the ceiling fan is quiet — even quieter than our air purifier running on its silent mode. It doesn’t cut through the earplugs. I don’t notice it.

At higher speeds it begins to almost chop the air like a helicopter. The higher speeds were a godsend during when the bedroom temperature hit a sustained 30 degrees.

The One Thing That’s Not Quite Right

Speed 1, the lowest setting, isn’t slow enough. There are six speeds, and 1 should be a gentle stir of air rather than a definite breeze.

There’s a partial workaround. If you reverse the fan direction so it pulls air up instead of blowing it down, the breeze sensation reduces because you’re not in the direct column of air. You still get the circulation benefit, just without the draught. Most of the time I leave it blowing down anyway. It’s not intrusive enough to bother me. But it would be nice to have a genuinely slow setting for sleeping.

It’s a small thing. But it’s the one thing I’d change.

What I’d Do Differently

Not much, honestly. The fan itself is fine. The installation frustration was mostly down to poor instructions, not the product, and once it’s up you forget about that.

If I were doing the install again, I’d offset the mount from the electrical supply from the start. And I’d loosen the cowling screws before assembling the fan onto the bracket. Two small things that would have saved me twenty minutes of swearing.

Is a Ceiling Fan Worth It in the UK?

For £120, yes. Unequivocally.

It’s solved a real problem (the south-facing room that wouldn’t cool down at night), and it’s done it quietly, without adding another thing cluttering up the floor. It doesn’t demand attention. It just spins and the room is better for it.

Would it replace air conditioning? Probably not, but it would likely mitigate the need for it. On a genuinely hot day, when the outside air is still and warm, moving air around only gets you so far. The room still needs proper cooling at some point. But as a stopgap, and as something that will likely remain useful even once I do get aircon installed, it’s hard to fault.

Part of me thinks ceiling fans should be standard in any UK room that gets a lot of sun. The logic is so straightforward (a large slow fan beats a small fast one) that it’s strange they aren’t more common. I suspect it’s a combination of British pessimism about summer and the fact that most ceiling fans look like they were designed in a municipal building in the 1980s. The newer ones, like this Philips, don’t have that problem. They’re not beautiful but they’re inoffensive, and the integrated light means they replace rather than add to what’s already on the ceiling.

If you’ve got a room that overheats and you’re on the fence, I’d say try one. It’s cheaper and less disruptive than air conditioning, and if it doesn’t solve the problem entirely it’ll still make the room more comfortable than it was.

You can find the Philips Olas ceiling fan on Amazon if you want to take a look at the model I went with.

Frequently Asked Questions

Are ceiling fans worth it in the UK?

I think so, particularly in well-insulated modern homes and rooms that get a lot of sun. UK summers are now hot enough often enough that a ceiling fan earns its keep, and at around £120 for a decent model it’s a fraction of the cost of air conditioning. It won’t replace aircon on the hottest days, but it makes a noticeable difference.

Do ceiling fans actually cool a room, or just move air?

It is said that they don’t lower the air temperature directly, which is true. However, they allow air to circulate better so if the windows are open and it is cooler outside they can help draw in colder air and mix it. Which can cool the walls and furnishings, so I would class that as cooling the room. Obviously, that requires it to be later in the evening when the outside has cooled.

Can you fit a ceiling fan to a plasterboard ceiling?

Ideally, You need to fix into a ceiling joist, or fit a wooden support board between joists to spread the load. A few specialist plasterboard fixings are rated for fans, but most aren’t, so check the spec carefully before relying on one.

Are ceiling fans noisy?

The Philips Olas I fitted is quieter than my air purifier on its lowest setting. At higher speeds you do start to hear the blades chopping the air, but for sleeping you’d never run it that fast.

How much does a ceiling fan cost to run?

Very little.

Why are ceiling fans uncommon in the UK?

Probably a mix of reasons: older British housing stock was poorly insulated and rarely overheated, summers were historically milder, and ceiling fans had a dated aesthetic association with shabby hotel bars. Newer designs from brands like Philips, Lucande and Ollyri have largely solved the looks problem, and warmer summers plus better insulation are starting to make them more relevant.

Back to top ]]> Heat pumps https://johnewbank.co.uk/ceiling_fans_in_the_uk/ Mon, 04 May 2026 23:00:00 GMT Hydrogen Boilers: The NOx Problem Nobody Mentions https://johnewbank.co.uk/hydrogen-boilers-the-nox-problem-nobody-mentions/

Without the hype

There’s a push in the UK, by some industries, to replace methane in the gas grid with hydrogen. Proponents claim it is clean, easy to produce, and CO₂ free, with nothing but clean water vapour released.

Ignoring, for a moment, the economic and practical challenges of producing, transporting, and storing hydrogen at grid scale, let’s entertain the idea. Suppose we did it. Suppose every boiler in the country was burning hydrogen tomorrow — what actually happens?

The fuel is only part of the story

Everyone knows that diesel engines produce NOx emissions, nitrogen oxides. What’s less obvious is where the nitrogen comes from. It’s not the fuel, but the air. When diesel combusts at high temperature, it heats the surrounding air enough to break apart N₂ molecules into individual nitrogen atoms. These atoms are highly reactive, and when they encounter O₂ they readily form nitric oxide (NO), which oxidises further to nitrogen dioxide (NO₂). Together, these are referred to as NOx.

The same thing happens in a gas boiler. Fuel doesn’t burn in pure oxygen. It burns in air, which is roughly 78% nitrogen and 21% oxygen. At moderate temperatures nitrogen is inert and passes through the flame untouched. But above about 1,300°C, the N₂ bonds start breaking apart and the same NOx-forming reactions kick off.

Diagram of hydrogen combustion, in which hydrogen and air enter a flame above about 1,300 °C; most of the hydrogen forms water vapour, but the heat also splits nitrogen, which combines with oxygen to form nitric oxide.

Burning hydrogen makes water, but the hot flame also turns nitrogen from the air into NOx.

This process is called the Zeldovich mechanism, and the key thing to understand about it is that NOx formation doesn’t increase gradually with temperature. It increases *exponentially*. A small rise in flame temperature produces a disproportionately large rise in NOx. Which brings us to hydrogen.

Why hydrogen releases more NOx than methane

Hydrogen burns *hotter* than methane. The adiabatic flame temperature of hydrogen in air is around 2,100°C, compared to roughly 1,950°C for methane.

That might not sound like much, but because of the exponential relationship between temperature and NOx formation, that 150°C gap translates into significantly more NOx coming out of a hydrogen flame than a methane one.

So why does hydrogen burn hotter than methane in the first place? It comes down to what the released energy has to heat up. When methane (CH₄) burns, each molecule reacts with two O₂ molecules to produce one CO₂ and two H₂O. A lot of the heat released goes into warming up the CO₂, which soaks up energy into its vibrational and rotational modes. Hydrogen combustion does not introduce carbon: 2H₂ + O₂ → 2H₂O. So there is no CO₂ to warm. Instead, the only combustion product is water vapour, so more of the released heat ends up as raw temperature rather than being spread across the products, and consequently results in a higher flame temperature and more NOx formation.

So is hydrogen really zero emission?

It’s true there’s no CO₂ at combustion. But there’s more NOx.

I’m sure manufacturers will engineer workarounds — SCR systems (AdBlue, essentially), exhaust gas recirculation, lean-burn designs. But at that level of added complexity it sort of defeats the purpose of condensing boilers, in that they are cheap to make and install. So it leads to the inevitable: why not just spend the money on nuclear power and heat pumps?

Back to top ]]> Energy Environment https://johnewbank.co.uk/hydrogen-boilers-the-nox-problem-nobody-mentions/ Thu, 16 Apr 2026 23:00:00 GMT Is Balcony Solar Worth It? https://johnewbank.co.uk/is-balcony-solar-worth-it/

Without the hype

Updated October 2026: plug-in solar went on sale in the UK on 27 August 2026. I’ve added real kit prices and paybacks, what a battery would add, and my calculator is now at solar.johnewbank.co.uk for anyone who wants to run their own numbers.

The UK government has announced balcony solar will be legal and available in shops soon, so I thought: is it actually worth it? The only way to really answer that is to look at my historical energy usage and how much the solar panel will generate. Fortunately, this isn’t particularly difficult. But before I do that, I’m going to explain some assumptions I made and a bit more about what balcony solar is.

What balcony solar is

It is a plug-in solar system that can connect to a standard socket without an electrician or grid notification. It is just solar panels connected to an inverter, connected to your plug socket. I’ve heard that it might be limited to around 800W, but this number hasn’t been confirmed. (Update, October 2026: it is now confirmed. A plug-in system can feed in at most 800 W, and kits are designed around that limit.) I would have thought it would make sense to limit to a higher figure, such as the peak output of two standard panels, currently around 1000W.

Unlike a rooftop installation, where an installer handles the angle and orientation, balcony solar is largely a DIY decision. You can mount a panel flat, tilted, or vertical – against a fence, on a balcony rail, or fixed to a south-facing wall. The angle matters more than most people expect.

For my location, the optimal tilt is roughly 35° from horizontal, facing due south. A vertical south-facing panel loses about 30% of its annual yield compared to that optimum. A flat horizontal panel loses less.

Estimated annual generation per kWp, south-facing, by mounting angle (Surrey)

Mounting angle matters more than most people realise. A vertical south-facing panel generates around 28% less annually than one at the optimal 35° tilt — but for a fence or balcony rail installation, it’s often the only practical option.

Daily generation per kWp through the year, south-facing, by mounting angle (kWh, 7-day average)

The vertical mount’s flatter seasonal curve is less disadvantageous in winter, when the sun sits low in the sky. The tradeoff is a notably weaker summer. Drawn in October 2026 from Open-Meteo’s irradiance data, because PVGIS, which the March charts used, is currently refusing requests; its yearly totals are within 3% of the figures above.

How you mount yours will depend on your balcony. If you’re mounting on a south-facing balcony rail, vertical is probably your only practical option, and it’s still worth doing. If you have a flat roof or garden, tilt it.

I would mount mine at the optimal 35°.

I’m only looking at facing directly south

The property I am at faces directly south, as does the balcony. Consequently, I’m going to face the solar panels south. If your property faces a different direction, then you would have to consider how that would vary your output.

How the Calculator Works

To work out whether a panel would actually save money, I pulled a full year of half-hourly electricity consumption data from the Octopus API – 17,500 data points covering every 30-minute slot through 2025. I then used PVGIS, the EU’s solar irradiance database, to generate a typical hourly generation profile for my location in Surrey based on 2021–2023 weather data, scaled to 1kWp installed capacity. From what I understand, the peak output of balcony solar is limited to 800 watts, but I don’t know if that is the inverter max or something else. So I have assumed it will be sold with 485W panels, which roughly rounds up to 1kW. So generation might be a bit over, but it’s good enough.

For the calculations, I looked at the electricity consumption for my previous year and the potential solar generation. I ignored batteries and exports, as I wanted to make it as simple as possible. I only offset my true consumption for each half-hour period.

There is no simulated load shifting, no battery, and no export, only self consumption.

My saving from having a 1kW array

Saving = (self-consumed kWh × import rate)

My import rate is 23.35p and is fixed for the next year, so the saving is simply

619.3 kWh x 23.5p Annual saving: £145.54

Generations and savings by Month

Month Consumption (kWh) Generation (kWh) Self consumed (kWh) Saving (£)
January 176.4 41.4 30.9 7.3
February 159.9 58.1 38.6 9.1
March 189.1 83.6 57.1 13.4
April 137.9 119.4 55.2 13.0
May 140.7 121.6 63.7 15.0
June 171.0 129.5 78.7 18.5
July 139.8 122.7 60.0 14.1
August 125.2 115.0 53.4 12.5
September 218.4 91.0 70.5 16.6
October 210.1 72.2 50.0 11.8
November 244.5 46.3 37.9 8.9
December 253.8 25.4 23.3 5.5
Total 2,167.0 1,026.2 619.3 145.5

Monthly breakdown — consumption, generation, self-consumed

For my usage pattern, a 1kWp south-facing 35° array generates 1026 kWh annually in this location. Of that, roughly 619 kWh gets self-consumed and around 400kWh is wasted. At 23.5p/kWh import and 0p/kWh export, that works out to about £145.5/year in savings.

Monthly generation from 1 kWp at 35°, south: used at home and not used (kWh)

The lighter portion of each bar is generation that can’t be used in the moment and gets exported at around 5p/kWh rather than displacing grid electricity at 23.5p. Summer months have the largest gap between what’s generated and what’s actually useful.

Payback

A reasonable balcony solar kit — 800W panels and microinverter, are said to cost around £400. At £146/year in savings, the simple payback is just over three years. For a single panel this is quite compelling, particularly since the system requires no maintenance, no installer, and can be taken with you if you move.

Cumulative saving against a £400 kit, at £145.54 a year

At £145 in annual savings, a £400 system pays for itself in under three years — after which it’s pure saving for the remaining life of the panel, typically 25+ years.

Considering there is no attempt in my usage to load shift towards periods of high solar generation. The payback period Is impressively short. Obviously this would vary depending on what tariff you are on, but considering what could happen to electricity prices this winter, I believe a year long fix with a £25 exit fee, is a good bet.

The broader point here is that balcony solar makes a lot of sense. The payback is potentially very rapid, though this depends how much solar is installed over the coming year and whether or not the grid is oversupplied! Perhaps the payback won’t be very good if everyone gets it.

Update: real kits, October 2026

Plug-in solar has been on sale since 27 August 2026, and prices are now real rather than “said to cost”. Octopus Energy sells two bundles, each with a microinverter and a plug-in cable: a single 460 W panel for £450 and two 460 W panels for £650. A price tracker of other retailers lists kits from about £340 for a single panel to around £1,000 for the largest.

I re-ran my 2025 usage through the same calculation as my calculator, with each kit’s output capped at 800 W. The cap barely matters: after losses, two 460 W panels peak at about 813 W and go over 800 W for only 7 hours across three years of weather data.

Kit Price Generated kWh/yr Used at home kWh/yr Saving, no export Payback, years Saving with Outgoing Payback, years
Octopus single-panel bundle (460 W) £450 470 382 £100 4.5 £111 4.0
Octopus dual-panel bundle (920 W of panels) £650 941 592 £156 4.2 £198 3.3

These use the current price cap of 26.32p/kWh. At my fixed 23.5p, the dual-panel bundle saves about £139 a year and pays back in 4.7 years.

Simple payback for my usage, at 26.32p/kWh

Two things have changed since March:

  • Export can now be paid, but only for Octopus’s own kits. If you buy the bundle from Octopus and Octopus supplies your electricity, you can join Outgoing Octopus, currently 12p/kWh (variable). You need a smart meter, and the kit has to be registered with the ENA and approved by your network operator first. Kits bought elsewhere can’t go on an Octopus export tariff. For the two-panel bundle, about 37% of what it generates goes back to the grid, so that payment cuts the payback from about 4.2 to 3.3 years.
  • Kits cost more than the £400 I assumed for two panels. The single panel is cheaper but generates half as much, and because more of its output is used at home, its payback ends up similar.

If you want to try this with your own usage, the calculator at solar.johnewbank.co.uk pulls your half-hourly data from your Octopus account and lets you change the size, angle, direction and tariff. If you’re switching to Octopus, my referral link gets you £50 credit.

What about a battery?

A battery isn’t allowed with a plug-in kit at the moment. The regulations that made plug-in solar legal define a plug-in device as one that is “not designed to import electrical energy … for the purpose of storing energy for later supply”, and the product specification requires kits to warn against using them with a battery. A battery would have to be a conventional installation, by an electrician. So treat this as a what-if, in case the rules change.

I modelled a battery that charges only from surplus solar and covers the home’s use when the panels can’t. That is the best a battery can do on a flat tariff. It uses the same assumptions as my calculator: 90% charging efficiency, 10% of the capacity kept in reserve, and charging and discharging limited to 800 W, as on plug-in-scale batteries.

Annual saving with a battery, by battery size (at 26.32p/kWh)

Battery (dual-panel bundle) Saving a year Extra from the battery Most it could cost to pay back in 10 years Extra, with Outgoing Most it could cost, with Outgoing
1 kWh £208 +£52 £525 +£26 £259
2 kWh £222 +£66 £661 +£33 £326
3 kWh £227 +£71 £712 +£35 £351
5 kWh £231 +£75 £752 +£37 £371
  • With one panel, a battery adds little: about £21 a year whatever its size, because a single panel rarely makes more than the house is using.
  • With two panels, most of the gain comes from the first kilowatt-hour or two. A 1 kWh battery adds about £52 a year and 2 kWh about £66, but going from 2 to 5 kWh adds only £9 more.
  • Being paid for exports makes a battery worth much less. On Outgoing Octopus, the surplus already earns 12p, so a 2 kWh battery adds only about £33 a year.

To pay for itself within ten years alongside the two-panel kit, a 2 kWh battery would have to cost under about £661 installed, or £326 if you’re being paid for exports. Until batteries are allowed with plug-in kits, the free way to capture more of the solar is to use it as it’s generated: run the washing machine and dishwasher during the day, as in the next section.

What If I could use all the energy I generated.

As a thought experiment, it’s worth asking what the numbers look like if I was able to use everything I generated, for a 1kW array it wouldn’t be challenging to self-consume more, by running the washing machine and dishwasher during the day, cooking things in the oven during the day, etc. I wouldn’t be able to use it all, but more of it.

Monthly saving from 1 kWp: actual, and if every kWh generated were used at home (£)

The gap between the two bars is essentially the value a battery would capture. At ~£96/year it would make the case for shifting daytime loads like dishwashers and washing machines into solar hours.

Month Generated (kWh) Self-consumed (kWh) Actual saving (£) Perfect saving (£)
January 41.4 30.9 7.3 9.7
February 58.1 38.6 9.1 13.6
March 83.6 57.1 13.4 19.6
April 119.4 55.2 13.0 28.1
May 121.6 63.7 15.0 28.6
June 129.5 78.7 18.5 30.4
July 122.7 60.0 14.1 28.8
August 115.0 53.4 12.5 27.0
September 91.0 70.5 16.6 21.4
October 72.2 50.0 11.8 17.0
November 46.3 37.9 8.9 10.9
December 25.4 23.3 5.5 6.0
Total 1,026.2 619.3 145.5 241.2
  • Actual annual saving: £145.54
  • Perfect self-consumption saving: £241.16
  • Gap (battery opportunity): £95.62

At 1,026 kWh generated annually, full self-consumption would save around £241/year at 23.5p/kWh. Against the actual figure of £145, that’s a gap of roughly £96. Payback in the theoretical case would drop to under two years.

What about Octopus Agile pricing? (draft) – will check again.

I’ve had a request or two about what would happen if I was on agile and whether vertical solar would make any difference. For AGILE-24-04-03 C (which I believe is London)

This is for a current price cap and historical agile prices, this is a somewhat flawed analysis. I fixed my price this year as I anticipate that prices will rise this winter. If they do then Agile prices will likely rise at times too. So using agile prices from 2025 to 2026 might be misleading.

Setup Agile Tariff Price Cap Tariff
Total Cost: No solar £416.59 £509.24
Savings: Vertical panels £88.92 £121.61
Savings: Optimal incline (35°) £107.77 £145.54
Total Cost: Vertical panels £327.67 £387.63
Total Cost: Optimal incline (35°) £308.82 £363.70

The usage figures in this article come from our Octopus Energy account, pulled half-hourly through the Octopus Home Mini and the Octopus API. If you’re thinking of switching, my Octopus Energy referral link gets you £50 credit once the switch completes.

If you enjoyed this article and want to say thanks or if you want to support heat pump experiments and new articles please support me here! https://buymeacoffee.com/ewbank

Back to top ]]> Energy https://johnewbank.co.uk/is-balcony-solar-worth-it/ Wed, 25 Mar 2026 00:00:00 GMT ProCook Elite Tri-Ply Pans Review (2026): 6 Months later + 15% Discount https://johnewbank.co.uk/procook-elite-tri-ply-pans-review/

Without the hype

Why I chose the Procook Elite Tri-Ply, and not the Elite Tri-Ply Signature.

Procook has two tri-ply ranges that are similarly priced. The normal Elite and the Elite Signature, shown below.

The ProCook Elite Tri-Ply range, polished stainless steel saucepans with glass lids and a frying pan.

ProCook Elite Tri-Ply, the range I bought.

The ProCook Elite Tri-Ply Signature range, brushed stainless steel saucepans with steel lids and a frying pan.

ProCook Elite Tri-Ply Signature, with its brushed finish.

I prefer the brushed stainless steel of the Signature range; however, the Elite Signature are noticeably shorter in stature, and therefore have less internal volume. I thought long and hard about sacrificing aesthetics for practicality, and choose the Elite Tri-ply set, as at the time I wanted more internal volume. In hindsight, I think I over thought this and could have just got a 24cm stockpot in addition to the 20cm saucepan.

Additionally, I was concerned that the stainless steel helper handles on the smaller saucepans of the Signature range might prevent them from stacking as well.

Feature ProCook Elite Tri-Ply Signature ProCook Elite Tri-Ply
16cm Saucepan & Lid Internal: 16cm/6.3in x 8.5cm/3.3in
Capacity: 1.5L		 Internal: 16cm/6.5in x 9.5cm/3.5in
Capacity: 1.9L
18cm Saucepan & Lid Internal: 18cm/7.1in x 9.5cm/3.7in
Capacity: 2.2L		 Internal: 18cm/7in x 11cm/4.5in
Capacity: 2.8L
20cm Saucepan & Lid Internal: 20cm/7.9in x 10.5cm/4.1in
Capacity: 3L		 Internal: 20cm/8in x 12cm/5in
Capacity: 3.7L
Frying Pan 24cm/9.4in x 5cm/2in 26cm/10in x 4.5cm/2in

What I Have and What I’d Change

Initially I had:

  • 16cm, 18cm, and 20cm saucepans and a 28cm frying pan from ProCook Elite Tri-Ply range
  • 30cm wok from John Lewis

With regard to the John Lewis pan, I received a voucher which is why I got that. It is a nice pan, but it is very heavy for a Wok especially with the angular handle. Does a wok really need to be tri-ply, I don’t know… I thought about getting a carbon steel wok, but decided against it for now. I think I would be tempted to get the Procook Wok if I was buying again and looking for a Wok as it has a nicer curved handle.

After a few months I found myself wanting a small saucepan a lot for things like rice. I also added the 22cm frying pan as I wanted something smaller to cook eggs and smaller things in. Finally, I bought a 24cm shallow casserole for things like meatballs and currys.

A ProCook 14 cm saucepan with a glass lid and a 22 cm frying pan on a white worktop.

The 14 cm saucepan and 22 cm frying pan I added later.

What I’ve Learned

I think saucepans are great, and useful. The Procook pans have grown on me and I don’t regret my purchase. Initially, I was a bit unsure. I would say that but sauciers (chefs/Saute pans) may have been a better purchase, perhaps I just need some separately. Saucepans are essentially pots: good for boiling things and stirring a bit. Sauciers (chefs pans) have curved, flared sides that allow for more even stirring and make it easier to reach food at the edges.

Update 14/04/2026: I no longer feel as strongly about sauciers, I will get one or two but the saucepans are performing well enough for my needs.

Would I Recommend These Pans?

Yes, the ProCook pans feel robust, they seem like they will last, and they clean easily. If you’re looking for a solid starting point, that is 3mm thick tri-ply and doesn’t cost the earth then I think they are a good choice.

You can probably get the similar results from a normal encapsulated-base saucepan for boiling and simmering. Where tri-ply makes sense is for frying pans, where even heat distribution makes more of a difference.

Update 14/04/2026: I am now pretty pleased with my purchase, given how well the pans perform and how much I use them I think it was worth the price.

Thickness of Tri-ply

Procook Elite as you can see it is around 3mm, my battery for the digital display has ran out. I will get a new one and post the updated image.

Digital calipers measuring the rim of a ProCook Elite pan, with the display blank.

The ProCook Elite measures around 3 mm at the rim (the calipers’ battery had run out).

John Lewis five-ply thermacore: Clearly much thinner barely over 2mm, this surprised me as it weighs a lot!

Digital calipers measuring the rim of a John Lewis Thermacore five-ply pan.

The John Lewis five-ply is barely over 2 mm.

Handle Comparison

A ProCook saucepan and a John Lewis pan side by side, showing the John Lewis handle's flat, angular profile.

The John Lewis handle is flatter and more angular.

As you can see the John Lewis handle is much flatter and more angular, you wouldn’t think this would make a big difference, but I find it does.

Top down view to show length

Top-down view of the ProCook and John Lewis pan handles side by side, showing their lengths.

A top-down view, to show the handles’ length.

Frequently Asked Questions

How do I get a ProCook discount code?

The simplest way is via a referral. Use my ProCook referral link, or type J Ewbank into the “Referred by a friend” field at checkout — both apply 15% off your first order.

Is ProCook Elite Tri-Ply worth it?

For me, yes. hey are sturdy, clean easily, and at around £40 per piece with the referral discount they are noticeably better-priced than John Lewis Thermacore at roughly £58 per saucepan. I expected that the insides would develop scratches over time, and they have (My girlfriend likes to stir with a fork). But that is why I bought stainless steel pans, because it doesn’t matter if they scratch. However, that is why the brushed steel of the Signature Elite-Tri-ply might be better

ProCook vs John Lewis Thermacore — which is better?

I own the ProCook saucepans and frying pans, plus a John Lewis Thermacore wok. The ProCook handles are far more comfortable — rounded and easy to grip — whereas the Thermacore wok handle is angular and digs into your hand. ProCook is also notably thicker (around 3mm vs roughly 2mm for the Thermacore five-ply). The Thermacore wok itself is excellent, but I’d choose ProCook for saucepans without hesitation.

Are ProCook Elite Tri-Ply pans dishwasher safe?

Yes, ProCook lists them as dishwasher safe, I only use the dishwasher and haven’t noticed any ill effects. One thing to note with stainless steel is that you shouldn’t wash it with aluminum as it can cause oxidation and rust of the stainless steel.

How thick is ProCook Elite Tri-Ply?

Around 3mm based on my own measurement of the base. The John Lewis Thermacore five-ply, by comparison, is barely over 2mm despite.

Do I need tri-ply saucepans?

Honestly, probably not for boiling and simmering, a decent encapsulated-base saucepan does most of what tri-ply does. Where tri-ply genuinely matters is frying pans, where even heat distribution across the sides changes how food cooks.

Back to top ]]> Reviews https://johnewbank.co.uk/procook-elite-tri-ply-pans-review/ Fri, 30 Jan 2026 00:00:00 GMT What Stainless Steel Pans should I buy? Which pans I purchased and Why. https://johnewbank.co.uk/what-stainless-steel-pans-should-i-buy-which-pans-i-purchased-and-why/

Without the hype

It’s fair to say that buying anything in the UK now is a mission. Most reviews seem like nonsense, marketing, or spam – and even companies like the BBC are taking revenue from selling products. See “BBC Good Food” recommending Tower pans.

With that in mind, let me talk you through my requirements for a pan.

Firstly, if I’m buying something like a pan, I don’t really care about the brand, I care about how long it will last. I also have a gas hob currently but may get induction in the future.

So what is the best material for a pan? There’s a very large trend for cast iron right now, but cast iron pans are heavy, can’t go in the dishwasher, need seasoning, and require careful maintenance. They’re also very poor at conducting heat. You might think “What? But metal is a good conductor of heat!” Not all metals are created equal:

Metal Thermal Conductivity (W/m·K) Notes
Copper 385-401 Highest conductivity; excellent heat distribution but expensive and reactive
Aluminum 205-237 Very good conductivity; lightweight and affordable; often anodized or clad
Cast Iron 46-52 Low conductivity but high heat retention; slow to heat, slow to cool
Carbon Steel 43-54 Similar to cast iron; popular for woks and skillets
Stainless Steel 15-25 Poor conductor; often used in clad cookware with aluminum or copper core

So logically, copper is the way to go. However, copper is not magnetic and doesn’t work on induction hobs. It’s also expensive and doesn’t like dishwashers. So that’s out. Aluminium also doesn’t like dishwashers – it’s the reason I’m replacing my current set of pans, as the aluminium base is dissolving.

Cast iron rusts and doesn’t go in the dishwasher; the same applies to carbon steel. So what’s left? Just stainless steel, but that has terrible heat conduction worse than cast iron.

Why does heat conduction matter so much? Heat conduction matter more for searing and frying rather than for cooking sauces, where you’re just maintaining a gentle simmer. The issue with cast iron is that it can get hot and holds that heat well due to its mass. However, when food is placed in the pan, heat is pulled out of the metal and into the food. The pan’s surface temperature drops and if the pan can’t conduct and transfer heat burner rapidly enough to replenish what’s being lost, it creates a temperature dip. So instead of a nice caramelised crust, the food steams in its own moisture. A pan with better heat conduction can recover more quickly, keeping the cooking surface consistently hot.

You might ask why carbon steel woks are good for stir fries if carbon steel has poor thermal conductivity? Essentially, it is because the metal is very thing and the heat doesn’t have to move though much metal to reach food. Woks don’t have flat bases and are unlikely to warp like saucepans and frying pans. But they are not what I am looking for.

So I am down to stainless steel which has terrible heat conductivity; however, there are a few ways to get around it.

  • Stamped base: The base of the pan is made of aluminium and stamped onto the stainless steel structure.
  • Encapsulated base: An aluminium disc is encased in stainless steel and stamped onto the structure.
  • Fully clad: The entire pan is made of layers of aluminium sandwiched between stainless steel.

The fully clad option is widely regarded as the best choice, as it allows the pan to be dishwasher safe while taking advantage of the heat conduction properties of aluminium.

This brings us to tri-ply. Tri-ply is this stainless steel and aluminium sandwich. There is also 5-ply, but that is in reality just tri-ply trying to sound fancier.

So I just get any tri-ply pan and I’m all good? That’s what I had hoped, but it turns out there’s more to this than meets the eye.

Thickness matters. We have come across cheap pans that have warped. This is a classic example of what happens with thin materials: one side expands or contracts faster than the other, which creates a force. That force creates stress in the material, and if sufficient, it can plastically deform the metal so it bends.

Unfortunately, most manufacturers don’t mention how thick their pans are. This is because they aren’t thick, they’re poorly made, and there’s a good chance they might warp.

There are other things to consider too. For example, is the lip of the pan encapsulated? This essentially means: are the outer stainless steel layers fully rolled over the aluminium core? If they aren’t, this can apparently cause delamination over time and the pan can start to break apart. My mum had her very expensive Le Creuset pan delaminate like this. Fortunately, she had bought it for 50p at a jumble sale, but she is still outraged.

Another consideration is whether the pan handles are welded or riveted. I initially read online that welded is better because dirt can get trapped in the rivets. However, I then looked at my current pans and saw that there was no dirt in the rivets. This stopped mattering to me.

After accounting for all of these factors, I set about doing some research.

I initially looked at Stellar Eclipse pans but couldn’t get my head around their pricing. I couldn’t figure out whether they were pretending to be good value by being perpetually “half price” or whether they were actually on offer.

I also looked at various pans in TK Maxx but came to the conclusion that they didn’t have the thickness I was looking for. If I was paying for new pans, I wanted them to last, and I would be willing to pay extra to ensure that.

I also looked at the BBC Good Food Tower Tri-ply pans but realised these were essentially an advertisement.

John Lewis Thermacore was another option, but I couldn’t bring myself to spend £175 on their 3-piece set. They do look very good, however. I visited the store to look at them and the pan they had in stock, a 28cm casserole, just didn’t seem robust enough for the money. Though I do like the brushed stainless steel finish as it doesn’t show scratches as much as polished stainless.

I also looked at Proware but they didn’t list the tri-ply thickness.

That covers most options for tri-ply pans in the UK, so I began I looped back around to ProCook again with the Elite tri-ply and ProCook Professional range, which have an encapsulated base. I had considered ProCook previously and had used my friend’s ProCook pans, which are good. However, I wasn’t sure which pan to pick as I didn’t trust the reviews, there is something about having many hundreds of thousands of Trustpilot reviews that doesn’t sit right with me. I previously found a company faking reviews, and have had Emma mattress request my review was deleted for essentially calling their product rubbish. They do this by requesting a response to the review, if you don’t respond within a few days it is deleted.

My fears were assuaged when I found this Reddit post:

Cookware Buying and Explanation Guide

It’s always quite satisfying to find a bunch of people who are far more nerdy than you about a certain subject and have thought about it for years. These people have thought deeply about what pans to buy. They’re mostly American, but ProCook was on the list under “Recommended High Tier Stainless Steel” for the reason that it is 3mm tri-ply: thick and not super expensive (obviously much more than a normal cheap stainless steel pan, mind you).

So I bought this set of pans. They are £195 at the time of writing; however, my friend sent me a 15% discount link which brought them down to £165. This is still expensive but more reasonable. If you want a discount on these pans, you can use my code: ProCook referral link.

You can also type J Ewbank into the “Referred by a friend” box at checkout for 15% off your first order over £30. The details are on my ProCook referral code page.

I bought that set because I wanted a reasonably sized stainless steel frying pan and because I wanted those three saucepan sizes. There is also the Procook Elite Signature which looks nicer and is brushed stainless steel instead of polished, but the are slightly squatter and I wanted the extra volume of the Procook Elite pans.

There are other ProCook sets which include stockpots and casserole dishes; however, these have narrow 20cm stockpots, which in my opinion is too small. A 20cm saucepan, yes. A 20cm casserole, no.

I might buy a chefs pan at some point, but haven’t decided which one to get yet.

A tip when buying pans: pull out your measuring tape and measure your own hands against what you are buying. I did this and it made me realise I had underestimated the pan sizes I needed. Also look at the dimensions on the web pages. Frying pans listed as 28cm might be 28cm at the top but only 24cm at the base, which is the area you actually cook on.

I bought the ProCook Elite Tri-ply cookware set because I have a gas hob. If you have an induction hob, you should probably consider the cheaper Procook Professional range instead. The reason is that they are cheaper, but also the base is very thick aluminium encapsulated in stainless steel. Induction hobs work by creating an oscillating magnetic field which induces an electric current in the metal. If the metal is very conductive, it doesn’t create much heat as there is very little resistance. The pan needs to be a relatively poor conductor of electricity, and therefore have high resistance, for the energy to be converted into heat. The thick encapsulated base also reduces vibrations and noise on induction hobs, which can be annoying. Heat won’t travel quite so well up the sides of the pans as with fully clad, but for the price they are more than adequate.

I haven’t done a full test of these pans yet. This is just a write-up of why I chose them. I’m going to do a proper test shortly.

This whole buying process has left me rather frustrated. There aren’t particularly good resources online, and most reviews seem absurd. If you read half the things on Reddit, the advice often boils down to “why don’t you just buy the most expensive pan available?” as if budget simply isn’t a consideration. There’s a strange snobbery around cookware where anything less than professional-grade is dismissed, which isn’t helpful for someone just trying to make a sensible purchase.

At the other end of the spectrum, mainstream reviews from publications and influencers are often thinly veiled advertisements. It’s difficult to find honest, practical guidance that sits somewhere in the middle: acknowledging that most people have a budget, while still caring about quality and longevity.

I hope this write-up is useful if you’re in a similar position. I’ve tried to explain my reasoning rather. The key takeaways are: look for tri-ply at least 3mm thick if you are using a gas hob or thick encapsulated bases if using induction. Though triply will still work well on induction.

Extra resources:

Back to top ]]> Reviews https://johnewbank.co.uk/what-stainless-steel-pans-should-i-buy-which-pans-i-purchased-and-why/ Thu, 22 Jan 2026 00:00:00 GMT Why Higher Fan Speeds Improve Air to Air Heat Pump Efficiency https://johnewbank.co.uk/why-higher-fan-speeds-improve-air-to-air-heat-pump-efficiency/

Without the hype

Higher fan speeds make your air-to-air heat pump more efficient. But why? What is the connection between moving air faster over the indoor coil and the compressor doing less work?

Most people know that lower flow temperatures in air-to-water heat pumps improve their efficiency, but not everyone knows why. The same is true for air-to-air heat pumps; increasing the fan speed results in higher efficiencies, but the reason behind this is rarely explained.

I am going to explain why this is the case through analogies and thought experiments, so you can intuitively understand the physics and how to take advantage of it.

*At lower heat loads fan speed doesn’t really matter it is only at higher heat loads that this becomes of concern*

Part 1: The Intuition (The Bicycle Pump)

To understand why fan speed matters, we need to understand what your heat pump compressor is doing. A good analogy is a simple manual bicycle pump.

Imagine you are pumping up a bicycle tyre. At first, the tyre is empty (low pressure), and the pump moves easily. You can push the plunger down with just one finger. You are moving air into the tyre, but it takes little effort.

As the tyre fills up, the pressure rises and it gets harder to pump. To push the same amount of air into the tyre, you have to use much more effort. Pushing against high pressure requires more energy.

This is the core of why higher condensing temperatures reduce heat pump efficiency. The heat pump compressor (like our bike pump) working against a higher pressure requires more effort, and therefore more electricity.

We will return to this analogy later. But first, we need to understand the journey of the refrigerant.

Part 2: How a Heat Pump Moves Heat (The Refrigeration Cycle)

A heat pump does not create heat; it moves it. It takes heat energy from outside and carries it inside. The refrigerant is the substance that carries this heat on its journey.

Choosing where to start the explanation of the heat pump cycle is difficult. I have chosen at the expansion valve but I could choose anywhere else. It is best to think of all steps happening at the same time, rather than sequentially.

Step 1: Expansion (The Spray Can)
The cycle begins with warm, high-pressure liquid refrigerant arriving at the outdoor unit. It passes through a component called the Expansion Valve.

Think of a can of deodorant or spray paint. Inside the can, the contents are at high pressure. When you hold down the nozzle, the fluid is forced through a tiny hole into the lower-pressure air outside. Two things happen immediately:

  1. It turns from a liquid into a mist (a mix of tiny droplets and gas).
  2. It feels incredibly cold.

As liquid deodorant expands it often pulls heat from the rest of the can, cooling it down.

The Expansion Valve acts exactly like that nozzle. It forces high-pressure liquid refrigerant through a tiny restriction into a lower pressure heat exchanger. As the refrigerant sprays out into the larger space of the outdoor heat exchanger, its pressure drops instantly, and its temperature plummets.

Step 2: Evaporation (Absorbing Heat from Outside)
The refrigerant is now an extremely cold, low-pressure mist inside the outdoor heat exchanger. A fan blows outside air over the coil.

Because of the expansion, the refrigerant is colder than the outside air. So heat energy naturally flows from the air into the refrigerant. This happens even on a freezing winter day, as anything warmer than absolute zero (-273.15°C) contains heat energy, so there is always some heat to collect – provided the refrigerant remains colder than the air.

As the refrigerant absorbs this heat, something important happens: it evaporates. It changes from a liquid mist into a pure gas (vapour).

This is where latent heat comes in.

Humans take advantage of latent heat when they sweat. When sweat on your skin evaporates and turns to gas and in doing so pulls heat from your body then floats off into the atmosphere. If it is very humid then sweat won’t evaporate as easily, so you continue to feel hot.

A similar principle applies to refrigerants. To change from liquid to gas, the refrigerant must absorb a large amount of energy. This energy is called latent heat, where “latent” means hidden, because this heat does not raise the temperature. The refrigerant absorbs a huge amount of energy from the outside air, but it does not get noticeably warmer. Instead, the energy is stored in the change of state itself.

By the time the refrigerant leaves the outdoor coil, it has absorbed as much heat as it can from the outside air. It is now a cold, low-pressure gas, perhaps only a few degrees warmer than when it started. Even though it is barely warmer it has absorbed and is carrying a lot of energy, but it is still too cold to heat your home.

Step 3: Compression (Adding Energy and Raising Temperature)
The cold gas now enters the compressor. This is the heart of the heat pump, and the component that uses most of the electricity.

The compressor squeezes the gas into a smaller space. When you compress a gas, it heats up. You may have noticed this if you have ever used a bicycle pump vigorously; the pump gets warm.

A more dramatic example is a diesel engine. Diesel engines have no spark plugs. Instead, they compress air so forcefully that it becomes hot enough to ignite fuel spontaneously.

Why does compression create heat? It comes down to the conservation of energy. Like with the bike pump, to compress the gas, the piston must apply a significant force to push the molecules closer together. It is doing mechanical work on the gas. That energy doesn’t just disappear; it is transferred into the gas itself.

As the volume decreases, the gas molecules move faster and collide more furiously. In physics terms, their kinetic energy increases – due to the work of compressing. Since temperature is essentially a measure of how fast molecules are vibrating and moving, this increase in kinetic energy manifests as intense heat.

In your heat pump, the compressor squeezes the refrigerant until it becomes hot: perhap just 30°C or maybe up to 60°C, or even higher. The cold gas that could not heat anything is now a hot, high-pressure gas that can warm your home.

For an air to air heat pump the compressor has to push the refrigerant against whatever pressure exists in the indoor coil. If that pressure is high, it takes more electricity. If it is low, it takes less. Just like our bicycle pump pushing against a full tyre versus an empty one.

The compressor pushes refrigerant against whatever pressure is in the indoor coil.

Step 4: Condensation (Releasing Heat Inside)
The hot, high-pressure gas flows into the indoor unit (the condenser).

A fan blows room air over the indoor heat exchanger. Because the refrigerant is hotter than the room air, heat flows out of the refrigerant and into the air, warming your home.

As the refrigerant releases heat, it condenses, changing from a gas back into a liquid. This is the reverse of evaporation, and it releases all that latent heat the refrigerant picked up outside, plus the energy added by compression.

The temperature at which this happens is called the condensing temperature. This temperature is critical to efficiency, as we will see.

Step 5: Back to the Start
The refrigerant is now a warm, high-pressure liquid. It travels back to the outdoor unit, reaches the expansion valve, and the cycle begins again.

Part 3: The Pressure-Temperature Lock

Here is the key insight: for a refrigerant at its boiling or condensing point, pressure and temperature are locked together.

This is just like water. At sea level (1 atmosphere), water boils at 100°C. On top of Mount Everest, where pressure is lower, water boils at around 70°C. Put water in a pressure cooker, raise the pressure, and it boils at a higher temperature.

Refrigerants work the same way. If the condensing temperature is high, the condensing pressure must also be high. If we can lower the condensing temperature, the pressure drops too.

And remember our bicycle pump: lower pressure means less work for the compressor.

Part 4: The Fan Speed Connection (The Puncture Analogy)

Now we can answer our question: why does fan speed matter?

Think of the indoor coil as a bicycle tyre you are pumping up, but with a puncture.

  • The compressor is the pump, pushing refrigerant in.
  • The heat escaping into your room is the air escaping through the puncture.
  • The fan speed represents the size of the puncture.

Low fan speed = Small Puncture.
Heat escapes slowly. To force the heat out through that “small hole”, the system must build up high pressure. High pressure means high temperature. The compressor has to work extremely hard to maintain this high pressure.

High fan speed = Large Puncture.
Heat escapes quickly. The “tyre” does not need to be highly pressurised to let the heat out. Pressure and temperature stay lower. The refrigerant only needs to be moderately warm because the excellent airflow whisks heat away efficiently.

Part 5: Why This Affects Efficiency

The important thing to remember is that, for a given compressor speed, the same amount of heat can be released into the room. But it can be achieved in different ways:

Scenario A: Low Fan Speed (High Condensing Temperature)

  • Heat escapes slowly into the room.
  • Pressure builds in the coil.
  • Compressor pushes hard against high pressure.
  • Each “stroke” takes more energy.
  • Result: Motor works harder.

Scenario B: High Fan Speed (Low Condensing Temperature)

  • Heat escapes quickly into the room.
  • Pressure stays lower.
  • Compressor pushes against less resistance.
  • Each stroke takes less energy.
  • Result: Motor works easier.

In both cases, your room receives the same amount of heat. But in Scenario B, the compressor used less electricity to deliver it.

This is the Coefficient of Performance (COP):

Same heat output, less electricity input = Higher COP.

Back to top ]]> Heat pumps https://johnewbank.co.uk/why-higher-fan-speeds-improve-air-to-air-heat-pump-efficiency/ Tue, 25 Nov 2025 00:00:00 GMT An Update on Air to Air Monitoring - Refrigerant Temps https://johnewbank.co.uk/an-update-on-air-to-air-monitoring-refrigerant-temps/

Without the hype

This project is occurring on someone else’s air-to-air heat pump. They very kindly (and very very foolishly) let me take it apart and faff around with it. As I have to travel to it, each visit is a learning process. So, I have an idea in my mind, only to find out that it doesn’t work or is nowhere near as easy as I had hoped.

It’s a bit like giving someone else a lecture on how to do something, mostly when you give unsolicited advice you don’t have a chance to find out your idea is terrible. Unfortunately, I have been on the receiving end of this terrible advice and taking it. So here is my documentation of failure – attempting to get reliable refrigerant temps off an air to air heat-pump.

Why I’m doing this

Refrigerant condensing temps relate to the COP. I want to know COP varies with fan speed. But also this is a secondary measurement for my mass flow COP estimates, it is always good practice have more than one point of failure. Many people achieve this secondary point of failure by getting married as it allows you to blame your other half.

Part 1. There is no space.

I have been struggling to get reliable readings from my sensors on the condenser and evaporator coils. One issue is that I’m putting sensors on a live unit, which—as you can see from the picture below—isn’t suitable for brazing (lots of plastic and refrigerant).

I can hear some people asking “Are you F-GAS”. My answer to that is don’t ask questions that I don’t want to answer. Plus I’m not doing any actual extraction of refrigerants.

Anyway. what began as a bit of a ‘bodge’ and a “hope this will work” is turning into a bit of an obsession. My first attempt was to place a DS18B20 inside an 8mm copper pipe – thanks to City Plumbing who sold me a single meter of it of it.

This might have been the shortest length of 8mm copper pipe they have ever sold. I should probably get some type of reward, maybe a display. In the store they asked me what I wanted it for; I paused briefly, then said, “It’s a bit complicated.” I thought they probably didn’t want to hear the entire story. I didn’t think I could give them a plausible answer.

Below is my attempt at wrapping this copper pipe to the copper evaporator coils (yes, HVAC installers, we are evaporating, and I’ll be in my cold hard grave before I call the external unit a condenser).

The connection was good and tight, and it was wrapped and insulated. But I didn’t get readings off it which I was convinced of. Copper is very conductive, stupidly so, you can test this by holding a piece of copper and heating it up with a soldering iron, you will quickly burn yourself. If you do the same thing with cast iron you will barely feel a tinge of heat.

A temperature sensor bound to a copper refrigerant pipe on the outdoor unit's heat exchanger with wound copper wire.

My first attempt on the outdoor unit, a sensor wrapped onto a coil pipe with copper wire.

The internal units presented even more of a challenge. As you can see, there is essentially no space to work. I say “no space,” but I can quantify that: there is exactly 0.35mm of space around some of the condenser end loops. Which equates to fuck all.

A fingertip against the tightly packed copper return bends at the end of the indoor unit's heat exchanger.

There is almost no room around the indoor coil’s return bends.

Some loops have a bit more space, which is how I managed to badly attach the sensor to them. By this point, I had exhausted my previous hopes of how I might attach my sensor. The space constraints were far more severe than I had hoped. I was just giving it a go to see what would happen.

A temperature sensor and its cable squeezed onto one of the indoor coil's copper return bends.

The first sensor, roughly attached to one of the looser bends.

After this, I went home and set about trying to fabricate a little clamp. The only copper I had was the one meter of 8mm diameter copper pipe, which I had to cut in half and hammer flat. This is objectively terrible – a bad workman blames his tools – but without a hard, flat surface to hammer onto, I don’t actually have any tools to blame. So I can only blame myself and I do so every time I look at this picture.

A small, roughly hammered copper clamp held in the palm of a hand.

My home-made copper clamp, hammered without a flat surface to work on.

Anyway, I tried it, but I had once again failed to appreciate how excruciatingly tight the heat exchanger is. I sort of wedged it in as a bodge to see what it would do once again. It was wrapped and insulated again too. As I expected it failed. I know it failed because my temperature reading for the air leaving the unit was always above the sensor temp. So I at least had a way to know whether my sensor was giving a good reading.

The copper clamp wedged between the indoor coil's return bends, with the sensor cable attached.

The clamp wedged into the coil.

Part 2 John Cantor sends me some bits

John Cantor kindly sent me over a couple of things: some spare copper sheet that he had been making solar panels out of in the 1980s, a little mount that he had made, and some more small TO92 sensors. The hope was that these additions would provide better readings.

I started with some relatively simple methods, such as wrapping the TO92 sensor in 0.35mm copper sheet to try and hold them near the coil, then insulating them. I didn’t actually want to use this approach, it is just that there was so little space I didn’t have a better plan at the time.

Fingers placing small sensors against the copper loops of the indoor coil.

Placing sensors next to the coil before insulating them.

I didn’t have high hopes for this method and didn’t get great results. Part of this was due to the sensor twisting—which I hadn’t seen until I looked at the photos later—but it was also likely due to a lack of thermal paste.

A sensor in a copper mount on the indoor coil, twisted away from the pipe, with its white cable running down.

The sensor had twisted away from the pipe, which I only noticed in the photos afterwards.

For the outside unit, he had brazed a little mount together. I don’t have a picture of this installed, but once again, I didn’t find my readings trustworthy. I now suspect that adding some thermal paste might assist in improving the readings. I will also get some liquid rubber to seal the copper components and the sensors from the external air before adding insulation.

Copper sensor mounts made from perforated copper strip, with a bolt and a pen on a notepad.

The copper bits John Cantor sent me.

Part 3 Starting my own foundry.

My girlfriend was out for the weekend, so I thought it would be the perfect time for me to begin casting my own metal parts on the hob. In this picture, you can see the 8mm copper pipe that an encapsulated DS18B20 can slide into.

Hamid Salimi of Daikin kindly organised some of the 6mm end loops to be sent out to me, which I put to good use. The aluminium foil was to stop the 6mm end loops from sticking to the solder it was there to cast around. As you can see, I made a little casting bath (this is a new technical term I have invented) from copper sheet. All I did then was chop up solder, pop it in the casting bath, and get it hot. It only took me a couple of goes to produce something that sort of worked. I say chop up, I poked it into the gaps I wanted to fill and watched it fall melt off the reel.

A small foil and steel mould on a gas hob holding a copper pipe section, with solder melted into the gaps.

Part 3, casting solder around a copper mount on the hob.

I didn’t have the right tools for cleanup—no Dremel to polish—so I had to live with the rustic aesthetic that the casting bath produced.

No, it’s not crack, I promise!

Rough cast solder sensor mounts on crumpled foil beside a copper pipe offcut.

The finished castings, rustic but working.

I now have a DS18B20 sensor in one of these mounts, which is working. However, I did have an issue when installing. It turns out the radii of the curves of the Daikin air-to-air unit are not the same as my Mitsubishi unit. Which, of course, means that the entire curve isn’t in contact with the surface – sort of defeating the point.

But we live and learn. The next step will be to take a mould of the Mitsubishi unit’s curve and fit some 6mm pipe to it. Then, I’ll try making a cast for that.

All in all, this has been quite a good learning curve (get it). I still need to get my own air-to-air unit so I can iterate faster.

This new cast sensor with thermal paste warms up faster than my air temp sensor below the unit—which is the right behaviour. I just need to fit a lot more of them and iterate on the design a little. But I have a cunning plan… TBC

Heating start-up on 24 November 2025: coil and outlet air temperature, and power

After start-up, the new coil sensor reads just above the air leaving the unit, which is the right behaviour.

Back to top ]]> Heat pumps https://johnewbank.co.uk/an-update-on-air-to-air-monitoring-refrigerant-temps/ Mon, 24 Nov 2025 00:00:00 GMT The Business Case for Nothing: Carbon Capture’s Manufactured Value https://johnewbank.co.uk/the-business-case-for-nothing-carbon-captures-manufactured-value/

Without the hype

Pencil sketch on grid paper of a stick figure running while holding, on a string, a large bubble full of banknotes, with smaller empty bubbles around.

A bubble full of money.

The mental inertia that grips the brains of carbon capture proponents has induced such a potent gravitational force that they risk sucking the rest of society into a black hole of lunacy with them.

You wouldn’t pay for lung transplants so you could keep inhaling asbestos. You’d stop the exposure. Carbon capture makes the same mistake: billions spent pumping CO2 underground while we continue burning fossil fuels, rather than building clean alternatives that make the problem obsolete.

This may sound absurd, but within this analogy lies the truth of carbon capture: a perverse dance of accounting that justifies absurd projects by manufacturing fines.

Real vs Manufactured Costs

A real cost produces real value. Building a nuclear power station costs money, but it generates electricity for decades – powering homes, businesses, and industry. The expenditure creates something tangible that improves lives. It is real.

A manufactured cost only exists because we created it. Carbon pricing, regulatory fines, compliance targets – all examples of manufactured costs. Artificial penalties developed with the spurious assumption that by penalizing a bad thing, that bad thing will somehow disappear or be solved.

“Put a price on carbon and carbon emissions will fall as releasing more carbon will cost more and therefore make companies less competitive.”

The idea seems logical – by putting a price on carbon, emissions will fall – but the intent masks the reality. Creating an artificial cost induces a “business case” for expensive solutions that produce nothing except the avoidance of that penalty.

Consider the Thames Tideway Tunnel: a £4.9 billion super-sewer built beneath London. The project was justified as “saving money for Thames Water customers.” However, no money was actually saved. Yes, the tunnel prevents sewage flowing into the Thames, and yes, that is good. But the business case was manufactured. The only thing the tunnel saved was self-imposed fines, reasoning that goes something like this: “For each hour sewage is discharged into the Thames I will charge myself £100,000, therefore if I build a super sewer I will avoid these costs and save money.”

Self-imposed fines are similar to thinking “If my car is older than three years I’m going to fine myself £400 a day, so I need to buy a new car next week.”

Yes, that’s a somewhat facetious example. But it highlights a point, we can justify any expenditure with frivolous logic, but that doesn’t make it right. It isn’t that the tunnel is wrong – it’s the spurious reasoning that accompanies it. The tunnel doesn’t generate electricity or produce clean drinking water; it creates no real utility beyond preventing a fine. The “value” is entirely manufactured by the regulatory framework.

The same pattern pervades government policy. ULEZ charges, congestion charging, Low Traffic Neighbourhoods – none of these make public transport better, faster, or more reliable. They simply make driving worse and more expensive. Low Traffic Neighbourhoods don’t create new infrastructure – they block existing routes. ULEZ doesn’t make buses better. Congestion charges don’t improve trains. The intention is to force people out of their cars by making the status quo worse, not by developing better alternatives.

This cuts to the core of current government policy: manufactured costs and difficulties are invented to make the status quo worse, not to make the alternative better. They are lazy solutions used to justify policy intentions.

The Carbon Capture Case

These regressive manufactured costs pervade ever more of our lives, but carbon capture represents their apotheosis. The core idea is that by connecting industrial emitters to depleted oil fields and pumping CO2 emissions underground, we will save both money and the planet. However, we don’t save any real money – we simply avoid self-imposed fines for releasing CO2. The outcome is accounting success, but everything else surrounding the process is madness. No electricity generated. No useful product created. Just carbon moved from one place to another, at enormous cost, because it has been assigned an arbitrary price.

I don’t want to pretend we shouldn’t reduce CO2, but carbon capture is simply rent-seeking behaviour dressed up as climate action. All of the effort, work, time and money combined to produce these carbon capture facilities could have been placed elsewhere. The money could be spent on something useful, something that results in something; nuclear power stations, train lines, housing – something tangible, something with permanence that can be sold, traded, used in the economy. Not merely buried to avoid a self-imposed cost.

There is a certain perversion to it all – a deep-seated inability to coherently understand the consequences of interacting policies. “Look at all the fines we’re avoiding, look at these industries that aren’t emitting carbon.” But there is no attempt to quantify the real ROI for carbon capture; it is all spurious.

Addressing the Counterarguments

“But climate change is real, and carbon imposes real costs on the environment.”

That might be the case, but if the US and China aren’t imposing carbon pricing, then the UK is poised for self-immolation at the spurious altar of moral good. This act of absurdity is analogous to Gordon Brown selling off the UK’s gold at record low prices – an instant reward, a feeling of doing good, but at the expense of destroying our own industries, offshoring jobs, reducing meaningful employment, and placing us in a state of subservience to the manufacturing hubs of Asia.

Playing hide-the-carbon doesn’t change anything globally; it just expends effort in the wrong direction while making British industry uncompetitive. Carbon border taxes won’t change this – any tariff will instantly result in reciprocal tariffs.

“We need all solutions, and hard-to-abate sectors require carbon capture.”

This reveals the circularity of the entire framework. Hard-to-abate sectors don’t need to be abated – they represent an insignificant amount of carbon released. They’re only “hard to abate” because we’ve created an arbitrary carbon price that penalizes them, forcing them to pursue abatement to remain competitive. Net Zero has become an accounting trick: carbon offsets, shuffling bits of paper, pretending to do something.

It isn’t real R&D. It doesn’t actually solve anything. It’s the dregs of a once productive oil field swallowed by a gaggle of gullible politicians.

Back to top ]]> Environment Energy https://johnewbank.co.uk/the-business-case-for-nothing-carbon-captures-manufactured-value/ Wed, 05 Nov 2025 00:00:00 GMT Underfloor Heating for a Suspended Timber Floor - on a budget https://johnewbank.co.uk/underfloor-heating-for-a-suspended-timber-floor-on-a-budget/

Without the hype

Recently, a friend of mine asked for some help with an underfloor heating system. He was renovating the property that he was planning on moving into and had received a quote of £15,000 for a system installation (without a floor on top), and we decided this was a bit of a rip-off.

Any underfloor system you install will add floor height, unless you dig down. This was not a problem for us as the door frames of the house were around 2 inches above the floor level. If your door frames are flush, then you might want to consider whether it makes sense for you.

Overlay isn’t the easiest thing to get your head around when coming from a place of zero background. There are lots of options, and I’m not convinced by the thermal outputs of most of them.

I had hoped that we might be able to use an egg crate system which allows for 16mm pipes at a 100mm spacing; however, the floor was suspended, and after calculating the dead load capacity of the floor, it was not feasible. Egg crates enable snail rather than serpentine laying of pipes (so they spiral in and out); the advantage of that is an even temperature across the floor. The egg crate system would weigh around 50kg/m² with a very minimal 25mm screed, so it was decided that the only approach was to use overlay.

Egg-crate panels, like these from The Underfloor Heating Store, hold the pipe between rows of raised studs, ready for screed.

Since I knew very little about overlay, I watched a few videos on underfloor heating and then rang up an underfloor heating company and asked for advice. I had already persuaded my friend to lay tiles on top of any system to improve heat conduction and the efficiency of the system, so they suggested using the cement-coated overlay panels. It was either these or foil-coated. They suggested the cement-coated panels are the more premium option and offer better thermal conduction, though I’m sceptical. I don’t really see how lots of heat would travel through such a thin layer of cement, but perhaps I’m wrong.

The cement coating meant that we could use tile adhesive to stick tiles directly to the top of the board without requiring a screed, so that seemed like the logical choice.

Heat Outputs- 20mm panel

ZL-CPS300-16 DatasheetDownload

Heat Outputs – 20mm Panel

ZL-CPS300-16 Datasheet Download

The website lists the following heat outputs at 50 degrees C, while the datasheet just lists 80W/sqm:

  • Under tiles: 97w/sqm
  • Under laminate, wood, engineered: 65w/sqm
  • Under carpet, vinyl: 51w/sqm

Which is right? I don’t know.

Wait, you didn’t do a full heat loss calculation?

I didn’t do a heat loss calculation as it was irrelevant to the build. The entire purpose of this underfloor heating installation was to get it in as soon as possible for the lowest price and the best reasonable specification. We weren’t actually doing a full system design. It was more about trying to reduce the cost of the future heat pump installation while maximising comfort.

I had done some basic calculations; I knew the system we planned to install had around 70sq/m of area and would produce around 3kW of heat at 40 degrees C with tiles.

Cement-coated XPS overlay boards with grooves routed for underfloor heating pipe.

The 20 mm cement-coated XPS overlay boards we used, from The Underfloor Heating Company.

A large room with grooved overlay boards laid over part of the timber floor.

Laying the boards.

Grooved overlay boards covering the whole floor of a bright room, with tile adhesive visible at the edges.

The boards down across the whole floor.

Fixing the boards down

I was told by the underfloor heating company to fix these down with tile adhesive – that is if you are putting tiles on top of. If you are using laminate on top of them you should use mechanical fixings. https://theufhgroup.co.uk/products/tekwarm-ufh-self-tapping-screws-and-washer-for-20mm-board-set-box-of-100-pcs

I had laid tiles before, but nothing this size. There was a small learning curve in applying the tile adhesive – this won’t apply to you as you won’t make this mistake.

After watching a few videos, I chose the following tool. As you can see, it has large curved cutouts. Generally, cutout size is in proportion to the tile size, so the bigger the tile, the bigger the cutouts.

A Vitrex professional notched trowel, with large curved notches along its edge.
The Vitrex professional notched trowel I chose, from Toolstation.

Since the tile trowel has ‘professional’ in its name, we believed it would elevate us to a higher standard of workmanship. Unfortunately, we had made an error, and having a ‘professional trowel’ didn’t make us professionals.

Another Important Point! Level the Floor Before Installing the Overlay!

After doing a fantastic job of installing the overlay, we patted each other on the back. Well done us. Then we got out the laser level and found out that our level plywood base that we installed onto was not, in fact, level in all places. But what is two centimetres of fall across runs between friends? It’s a 1 in 200 fall, so not much really.

We would have to rectify this error later. We had initially thought we could just level by using tiles and tile levelling pegs https://www.screwfix.com/p/no-nonsense-tile-levelling-system-kit-201-pieces/609PG?tc=KT8&gStoreCode=KT8&gQT=1 However, I would soon find this was not an option.

The grooved overlay boards across the floor, with tools lying on them.

The boards weren’t level, which we had to put right later.

Time for Some Polypipe

The pipe we installed came in 300m runs and was relatively easy to install once we figured out the technique, which turns out isn’t carrying 300m of pipe and unravelling it by spinning it in mid-air. Rolling it is better—who knew! As you unravel it, you have to turn with the corners; this is fairly easy and logical once you figure it out.

Important!

How long should your runs be? Most documentation online states the maximum length that your pipe runs should be (leaving then returning to the manifold) should be 100m with 16mm pipe. This is a limit not a target, I wish I had thought more about it before installing.

We ended up with four equal length runs of 90m each. However, if I were doing it again I would have dropped down to 60m or even 50m. This is because the temperature difference between the flow and return would be less so the temperature drop across the floor would be less. It would require a larger manifold but there would be a reduction in pressure loss.

Underfloor heating pipe laid in the grooves of the overlay boards across the room.

The pipe laid into the boards.

Now is the time to do a pressure test

You will need to connect up your pipes to the manifold and check for leaks. This part isn’t shown because it wasn’t done. My friend didn’t want to buy the manifold yet, what a gamble.

“Those Aren’t Tiles; Those Are Laminate”

A ordering error that made life a little challenging. While tiles had been specified, laminate had been ordered. This was a problem as it reduced the thermal conductivity. This was unfortunate, but since I had assumed we might need to put a radiator somewhere, I was not particularly bothered.

However, if I had known that we were using laminate, it would have meant we didn’t have to use tile adhesive to fix the overlay down instead could have used mechanical fixings.

“What Do You Mean There Is No Latex in Latex Screed!”

Since our floor wasn’t level and we wanted to maximise conduction of heat from the polypipe to the floor, we decided to lay a thin screed. While you might believe that ‘self-levelling’ screed is, in fact, self-levelling, it isn’t. So it won’t magically find the lowest point in your floor unless you are pouring a thick layer. It is, however, very liquid and easy to lay.

We spent a lot of time trying to figure out what the most appropriate type of screed to use was. The choices are either fibre-reinforced or latex-based. I couldn’t figure it out, so I rang up one of the companies that makes it, who told me ‘there is no latex in latex screed’. So I decided to make the executive decision and use my civil engineering background. I know that concrete has very little tensile strength, which means it is bad in bending unless it is reinforced with steel. I couldn’t see why a thin layer of screed wouldn’t be similar, in that it would have very poor tensile properties. Since we were going to try and do a thin layer across the floor with a bit deeper in places, I wanted some tensile strength in case the floor moved and expanded. So we went for fibre-reinforced rather than ‘not actually latex’ latex screed.

If your floor is flat, you can use dry screed overlay for thermal mass: https://www.insulationuk.co.uk/products/fermacell-r-flooring-2e11-1500-x-500mm-x-20mm

Get a Paddle Mixer

You will need a paddle mixer—a drill paddle mixer is not suitable. You need an actual one. For example: Energer ENB768MIX 1200W Electric Paddle Mixer 220-240V. I didn’t get this one; I borrowed a friend’s old DeWalt one, but they are similar.

I wouldn’t recommend a battery one as if you are mixing 40 bags of screed, then you won’t want to be waiting for batteries to charge. You are meant to mix each bag for 2 minutes, so you would need a lot of batteries.

Factor in the Pipe Cutouts

In the overlay, there are gaps where you haven’t put pipes. You can either fill these with pipes, or they will fill with screed. The amount of screed that they will require to fill is significant, so remember to calculate it. We didn’t, so had to make a few trips to Screwfix.

Remember to Prime the Overlay Boards

If you are going to put a screed over your overlay boards, then it is recommended that you prime them. This is apparently to improve adhesion and reduce cracking.

Tips on Laying a Levelling Screed

Three people is optimal. If you are doing it from bags, then you will need three people and two buckets. One person to put down the screed and roll it with a spiky roller. This helps remove air bubbles and lets the fibres line up (if using fibre-based screed).

Another person will need to mix with the paddle mixer, and the other prepare the water and add cement when mixing. You don’t need to do it this way, but it worked well for us.

A spiked roller knocks trapped air out of the self-levelling compound; Bostik explains how.

Freshly poured, glossy grey self-levelling compound covering the floor and pipes, seen through the patio door.

Self-levelling compound poured over the pipes.

The wet self-levelling compound across the whole room, reflecting the windows.

The whole floor levelled.

Next Up: The Floor

That’s it! The next photos are putting down a floor. We faffed around debating what type of overlay to install and how it would affect the conduction from the floor to the laminate but decided it didn’t really matter. So we went for a cheap option from Screwfix. This was a budget installation after all! I wanted to minimise the insulating properties of overlay there were some options which had cutouts, but I wasn’t convinced it was any better.

Parquet-pattern flooring being laid over the levelled floor, with the patio doors open to the garden.

Laying the new floor.

More of the parquet-pattern floor laid, with planks and packaging around the room.

Most of the way there.

The finished parquet-pattern floor, with a dog standing on it.

The finished floor.

Total approximate costs

Material Quantity Unit Size Unit Cost Cost per sqm Total Cost
Overlay Panels 70 sqm (98 boards) 1200x600mm boards £13.00 per board £17.81 £1,246.56
Tile Adhesive 10 bags Standard bag £13.00 per bag £1.86 £130.00
Polypipe 600m Standard pipe £0.73 per meter £6.29 £440.00
Self Levelling Screed 40 bags Standard bag £15.00 per bag £8.57 £600.00
Total £34.52 £2,416.56

Note: Cost per sqm calculated based on 70 sqm total area for all materials.

Underfloor Heating Systems Terminology

Term Definition Key Considerations
Overlay System Insulated panels installed on top of existing subfloor to house heating pipes Adds 20-40mm floor height; suitable for suspended timber floors with limited load capacity
Subfloor The structural floor base (typically plywood, OSB, or floorboards) that supports the heating system Must be level and structurally sound; existing subfloor may need reinforcement
Chipboard Routed Subfloor Pre-routed chipboard panels that replace existing subfloor, sitting directly on joists with integrated pipe channels More structural but requires complete subfloor replacement; minimal height addition
Screed Liquid cement-based layer poured over pipes to provide thermal mass and level surface Self-levelling but not truly self-levelling; requires 2+ people for installation
Egg Crate System Polystyrene insulation with pre-formed channels allowing snail/spiral pipe layout Provides even temperature distribution but adds significant weight (~50kg/m² with screed)
Serpentine Layout Pipe installation pattern where pipes run back and forth in parallel lines Simpler installation but can create temperature variations across floor
Snail/Spiral Layout Pipe pattern where flow and return pipes spiral together from outside to centre More even temperature distribution but requires egg crate or similar channelled system
Manifold Central distribution unit that connects multiple pipe loops to the heating system Size depends on number of circuits; affects pressure loss and flow balance
Flow and Return The hot water supply (flow) and cooled water return pipes in each heating circuit Temperature difference affects floor temperature uniformity
Dead Load Capacity Maximum weight a suspended floor can safely support Critical for suspended timber floors; limits choice of heating system type
Thermal Conductivity Material’s ability to transfer heat effectively Higher conductivity materials (tiles) improve system efficiency over insulators (carpet)
Pipe Runs Individual circuits of heating pipe from manifold out and back Maximum 100m for 16mm pipe; shorter runs provide more even temperatures
Cement-Coated Overlay Insulated panels with cement surface allowing direct tile installation Premium option that eliminates need for separate screed under tiles
Foil-Coated Overlay Insulated panels with reflective foil surface Standard option requiring additional screed or direct mechanical fixing
Mechanical Fixings Screws and washers used to secure overlay panels when not using adhesive Required for laminate floors; avoids adhesive mess and chemical off-gassing
Tile Adhesive Cement-based adhesive used to fix overlay panels and tiles Dual purpose: secures panels and provides base for tile installation
Pressure Test Testing pipe circuits for leaks before covering with screed/flooring Essential safety check; requires manifold connection and pressure testing kit
Fibre-Reinforced Screed Screed containing synthetic fibres for tensile strength Better for thin applications and areas prone to movement/expansion
Prime/Priming Applying bonding agent to overlay boards before screeding Improves adhesion between screed and boards; reduces cracking risk
Thermal Mass Material’s ability to store and slowly release heat Higher thermal mass provides more stable temperatures but slower response

Back to top ]]> Heat pumps https://johnewbank.co.uk/underfloor-heating-for-a-suspended-timber-floor-on-a-budget/ Mon, 19 May 2025 23:00:00 GMT