Most efficient window AC set up

May 18, 2021 2:43 PM

From an efficiency perspective, is it better to cool a small apartment with one larger window AC or two smaller window ACs?

Already have one AC in the bedroom. Given that I'm working from home, it is time to bite the bullet and extend the cool into the living room.

Current AC is 5k btu. We could:

- buy another of a similar size and have one at each end of the apartment
or
- get a 10k one that is large enough to cool the whole apartment and keep it in the bedroom

Other details--
-3 main rooms, maybe 600 sq ft, dog bone kind of layout with the bedroom connected to the living room via the kitchen, with two doors on either side of the kitchen... not an open floor plan by any means

-in a typical day for as long as wfh persists we would probably have both going for most of the day, and then only the bedroom one going at night

- don't need it to be too, too cool. Usually set the temps at 72 or 73

- I like to have my windows open when I can. All other things equal, if I didn't have to take another window out of commission by putting an AC in it, I'd prefer that.

posted by geegollygosh to Grab Bag (11 answers total)

I had a 10000BTU in a bigger apartment but found that it didn't really cool much beyond the bedroom it was in. However, the bedroom and living room were side by side, so it would have to bend corners to get in there. A fan helped but not a lot. You'd have to look at air flow. Maybe try putting a fan in the bedroom, and see if you can feel it in the living room.
posted by Ftsqg at 2:46 PM on May 18, 2021 [1 favorite]

Yeah the rooms matter as much as the BTUs. I’d guess two smaller is far far more efficient precisely because you won’t always need both running.
posted by spitbull at 2:54 PM on May 18, 2021 [4 favorites]

if I didn't have to take another window out of commission by putting an AC in it


There are some interesting new window ACs that use inverters and are quieter and more efficient. There are also some interesting U-shaped and inverted-U-shaped designs which allow you to open the window still. I'm not recommending either as I've not used them, but the new designs are clever.
posted by soylent00FF00 at 3:12 PM on May 18, 2021 [8 favorites]

There’s the fact that window ACs depend on internal thermostats. If the immediate area around your big AC is cooled to the proper temp, but the far side of the house is not, the AC will shut off anyway. You’ll have much finer control of the temperature with much more energy efficiency from not having to turn the big AC up to max so that the area around it is freezing and the far side is comfortable.
posted by ejs at 3:13 PM on May 18, 2021 [4 favorites]

I would go for option 2 because option 1 would be less efficient, making your bedroom freeze just to feel a bit of cool in your living room.
posted by oxisos at 3:55 PM on May 18, 2021 [1 favorite]

Response by poster: There are some interesting new window ACs that use inverters and are quieter and more efficient. There are also some interesting U-shaped and inverted-U-shaped designs which allow you to open the window still. I'm not recommending either as I've not used them, but the new designs are clever.

Oh nooo, haha, now I've fallen in love with a $400 dollar air conditioner.
posted by geegollygosh at 3:57 PM on May 18, 2021 [2 favorites]

Air doesn't move between rooms enough to make the one unit plan satisfactory.
posted by SemiSalt at 6:17 PM on May 18, 2021

I have the inverted U one in my office and it’s great so far. In fact I’m buying a second one right now for my daughter’s bedroom. Just be sure that it’ll actually fit in the window that you want it to fit in- 11 inches is surprisingly small.
posted by rockindata at 6:31 PM on May 18, 2021 [2 favorites]

An air conditioner that's too big for the space can make problems (it cycles on and off more than they're designed to), and it sounds like a 10K btu air conditioner being used only in your bedroom at night (with the door closed, I assume?) might functionally be "too big for the space."
posted by needs more cowbell at 2:52 AM on May 19, 2021 [1 favorite]

If you need an A/C in two different rooms, you can also get a portable rolling air conditioner.

You have to have them close to a window to drain the condensation and hot air, but they work great and are way easier to install and remove than a traditional in-window AC. They also take up floor space.
posted by The_Vegetables at 7:50 AM on May 19, 2021

If you are even remotely interested in efficiency, I strongly recommend staying away from portable/rolling air conditioners (the kind you hook up to a window with a hose). Those things are terribly inefficient compared to any window air conditioner. Some of the two-hose portable units are more efficient than the one-hose units, but even the best of those is going to be much less efficient than a window unit.
posted by Juffo-Wup at 10:27 AM on May 19, 2021 [1 favorite]