A concept for an outdoor only Air-to-Air Heat-pump
Recently, I’ve been thinking about all-in-one heat pumps like the Panasonic RAC Solo and the electriQ iQool. I experienced the latter while on holiday in France. These systems are single, self-contained units, much like portable air conditioners, but unlike portable aircon units, they have separate air intakes and out-takes that both draw from outside. This allows them to function like a true heat pump.
While these units are decent, they have drawbacks that got me thinking: why not flip the concept and create outdoor-only air-to-air heat pump units?
Essentially, what I’m suggesting is that instead of using a traditional split system, we place the entire system outside and duct the air indoors.
What’s Good About All-in-One Units
The Panasonic RAC Solo is a compact unit with a depth of just 165 mm. It ducts air from outside to the indoor heat exchanger and back out again, eliminating the need for a separate outdoor unit. What makes these units interesting is how straightforward they are to install. You don’t need to be a plumber or hold an F-gas certification to fit them. All it takes is drilling a couple of holes through the wall, connecting the ducts, mounting the internal unit, and wiring it up.
Where All-in-One Units Fall Short
The concept, while promising, is currently flawed. This is primarily due to the limited volume of air that can pass over the evaporator, which restricts heat exchange. This limitation stems from the units being mounted indoors and having to duct air inside, preventing the use of a large fan to blow air over the evaporator. As a result, they’re relatively inefficient compared to split aircon systems and struggle with large temperature differences between indoors and outdoors. When it’s cold, the evaporators can freeze up quickly—something I’ve seen mentioned in forum posts. The electriQ unit I used in France struggled to keep the small room I was staying in cool. So, while the concept is intriguing, I don’t think these units can ever be truly effective.
My Solution: Outdoor-Only Units
Why This Is Better
Instead of squeezing everything into a limited indoor space and dealing with a restricted volume of outside air for heat extraction, placing the unit outside allows it to function like a traditional mini-split with ample airflow and volume through the evaporator.
It also has the added advantage of blending in cold outside air to provide ventilation to the house if the unit detects excessive humidity levels.
It Makes Installations Cheaper by Eliminating the Most Expensive Part
An outdoor-only air-to-air heat pump retains the performance of a mini-split while keeping the advantages of an all-in-one unit—namely, that the installer doesn’t need to be a plumber or F-gas registered.
Why This Matters
From my own tinkering with heat pumps, I’ve seen how small changes can make a big difference. When I double-insulated the refrigerant lines on the air-to-air unit I installed, I noticed a significant drop in electricity demand. An outdoor-only unit with a larger heat exchanger could achieve similar gains. It eliminates losses along the chain while also reducing the potential for installer error.
Final Thoughts
All-in-one units like the Panasonic RAC Solo and electriQ iQool are great concepts that make heat pump technology accessible with their simplicity. But their limitations—low power, noise, and smaller evaporators—hold them back. An outdoor-only air-to-air heat pump could combine the best of both worlds: the ease of installation of an all-in-one unit and the efficiency of a traditional split system.
