This is more of theoretical question, not a practical, but it might be useful for some (we already have a system). I live around Auckland, NZ where heat pumps are very popular, typically ran for about 4-5 months a year. They are useful for about 2-4 weeks a year as air conditioner as well, but not absolutely essential.

Most popular system here is split system with some offering fireplace style indoor unit - which makes total sense as heat travels up so your split unit takes way longer to heat up the room.

To me tho sounds it might be simpler to just install window units mounted level to the floor. They are typically much cheaper and don't require extra piping for refrigerant.

BTU's aside, am I missing something why this wouldn't or couldn't be done?


6 Answers 6


The mounting hardware is different, but the principles are the same

What you're describing is called either a through-the-wall (TTW) or packaged terminal heat pump (PTHP). The two differ in physical form factor, with PTHPs being lower to the ground/squatter than a unit marketed as TTW, but the concepts and operation are essentially the same for these units as they are for a window unit.

PTHPs are commonly seen in multi-unit buildings, especially where units are small, such as hotel/motel rooms or efficiency apartments. Their TTW counterparts aren't as common, but can sometimes be found in applications where PTHPs are used, and also are handy for providing a packaged HVAC solution for outbuildings.


You state "I've updated title to be more direct - I'm talking about window units that are also heat pumps, not "regular" AC's.". They should work OK, they do not care if there mounted in a window or a wall. I had a neighbor do something similar, placing it through the wall, a while back with regular ACs but they were for cooling not heating. Just be sure to properly take care of the water etc that will come out during cooling. Since they are also heat pumps they will automatically do the defrosting. Check with the manufacturer they may offer a wall mounting kit.


Window air conditioners do not heat air, they take room air and cool it, exhausting warm air usually outside. If you could exhaust the cool air to the outside, they might output some warm air into the room. Doubt it would be enough to raise temperature enough.They are not reversible, so they cannot heat cool air.

  • Is that ground truth or they are less efficient at that? Because first Google search takes me to units that are indeed heat pumps: homedepot.com/p/…
    – dzh
    Jul 26, 2021 at 1:13
  • Window ACs and heat pumps are two different things. They are advertising window heat pumps the work as air conditioners and heaters. Straight ACs do not have heaters I read your at first asking about window AC units only, I might have miss read the question.
    – crip659
    Jul 26, 2021 at 1:26
  • For your edited question, you still need to exhaust or intake outside air. If you make ducts to go outside, it should work with some reduction of efficiently due to extra duck work. With whole unit inside, will also need to put up with extra noise.
    – crip659
    Jul 26, 2021 at 1:32

You can

There's no law requiring windows to be a certain distance from the floor. Build a low window and install the unit low down. you'll probably want it slightly above the floor to avoid accidental broom/kick damage.


The window a/c only units I have used are so noisy as to be unpleasant and for some people irritating in the extreme. They block the window and would likely prevent prevent the use of that window as a fire escape. They are the cheapest way to cool a room.


Since you've updated that they are actual heat pump units, not just cooling units, it should actually work ok.

Install will be a bit more work as you need a bigger hole in the wall and a decent seal so you don't get cold drafts in the winter. My main concern would be that the window units are likely cheaper because they're not built as well. Meaning you might end up going through a few window units over the lifetime of a better split system. I suspect efficiency would also suffer in the smaller window units.

For what it's worth, I know at least one person running that kind of setup for air conditioning. Works ok but it's much noisier than a split unit.

  • I've updated title to be more direct - I'm talking about window units that are also heat pumps, not "regular" AC's. That said I'm open to knowledge of whether they are inferior for that task!
    – dzh
    Jul 26, 2021 at 1:15
  • Thanks the update, that makes a large difference. I will update my answer then.
    – Olivier
    Jul 26, 2021 at 16:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.