Should I get a window a/c for the bedroom even if we have central air?

July 17, 2013 8:47 PM

We have a 2000sqft house with central air. We are fine keeping it at 76 or warmer during the day, but like a cold bedroom at night. Surely getting a window unit for our bedroom and closing the door makes more sense than cooling down the whole house at night. Even if we did close all the nonbedroom registers every night--which would be a chore I'd rather avoid. Is there any downside to this I'm not appreciating? Ot would it make no difference to our bill? Woulf it put less wear and tear on our central unit?
posted by elizeh to Home & Garden (10 answers total)

Do you have a ceiling fan? They make you feel a few degrees cooler. Closing registers may not be a good idea
posted by IanMorr at 9:01 PM on July 17, 2013

My family did this when I was growing up. We had central air yet the four bedrooms had wall units. My mother claimed it was a significant savings in terms of electricity and dollars. I do not have the facts or figures to back it up, but I do know my parents spent many hours on the phone with our local electric company negotiating and trying to find ways to lower our bill.

I would call your electric company and discuss it with them. They will give you accurate information or at least tell you how to calculate it. I know we got the above mentioned advice as well as peak and off peak rates. My mom would do the wash at 11:00 at night so that it was during a specific period of rates.
posted by JohnnyGunn at 9:02 PM on July 17, 2013

How old is your central unit, and what percentage of your summer bill is the air conditioning?
posted by sbutler at 9:10 PM on July 17, 2013

We do this. Terribly inefficient heat pump, and the upstairs of our house gets hot even if it's on. Downstairs stays at 80 overnight, bedroom is a nice cool 76.
posted by supercres at 9:14 PM on July 17, 2013

We do this, but I can’t help you with the cost factor, I’ve never tried to figure it out. It just seems to make sense since I want the bedroom colder than I’d ever want the rest of the house. Also, the bedroom is upstairs which makes it harder to cool with the central unit.
posted by bongo_x at 9:15 PM on July 17, 2013

just chiming in to recommend a ceiling fan as well. i have one in my bedroom and i've never had to put it on high, just the medium level, and it is quite quiet. my mom has central air but one room heats up more than others, the lanai, so she had a really nice-looking ceiling fan installed there and it has saved her a bundle as she hangs out in that room every evening. it's a large room too.
posted by wildflower at 10:06 PM on July 17, 2013

We do this. It works great. During the day we keep our house at 78. At night I essentially turn off the central air and turn on the window unit. I also put a towel next to the door so cool air doesn't leak out from under it. The white noise from the AC and the super cool air makes for great sleeping during the hot Florida summer. It would cost a fortune to cool the whole house to the temps we like for sleeping.
posted by Crotalus at 11:45 PM on July 17, 2013 [1 favorite]

I'll just say that if you're up for the installation costs given you already have central air, mini-splits are the, uh, "hot" new thing in air conditioning. Basically a ductless, air-sourced heat pump, they're ideal for areas that don't get much benefit from your central air and lend themselves naturally to zone control. Some considerations from Fine Homebuilding.
posted by dhartung at 3:38 AM on July 18, 2013 [3 favorites]

We do this in our house, mostly because our central air gets the main area of the house (kitchen, living room, dining room) cool, but the three bedrooms in the back of the house were always roasting. Plus we like to be slightly chilly when we sleep. So we got a few window units and they work really well keeping those rooms cool at night. It does save you money if you turn the thermostat for the central air up at night. When we sleep/retire to our bedrooms we turn it up to like 82 and just stay cool in our rooms with our individual ACs. Honestly it's just nice because everyone can have it as cool as they prefer for sleeping. You'll want to make sure you get the right size AC for your bedrooms. If you get something too big (too many BTUs), it's a waste of money, both in what you pay up front and in energy costs. Likewise, if you go too small, you'll also waste energy because it'll have to run constantly to cool the room.
posted by katyggls at 8:40 AM on July 18, 2013

A side note to consider: the house we are in doesn't have an air conditioner, so I had no choice but to buy window units. However, the windows all open horizontally, not vertically, so installing the window units was annoying. I had to make sure the window unit would fit in the horizontal space, then measure the empty space above the air conditioner and cut plywood to fill the gap. Then I used duct tape to seal the edges of everything.

So if you have horizontal windows, expect it to be more challenging.
posted by tacodave at 4:08 PM on July 18, 2013