A/C During the day (apartment, renting, house)

[rogetsthesaurus]

If you're gone all day M-F from 7:00 a.m. until 4:00 p.m., is it better to turn your AC off all together or set it to 85 or 90? I'm in a 1 BR apartment, ground floor, and keep it at 75 at night...but wonder why I should even have it on during the day...I heard it's worse to turn it off and on each day than to turn it up to 90 when you're gone (but then I'd never have it off...)

[Suzer]

A great question ... I hope we get responses here.

[joninaz]

It's better to leave it on, though you can raise the temp during the hours you are away. If you like 75 at night, let it go up to 85 when not there.

If you turn it off completely, the system will likely have to work a lot harder (wear and tear on the AC unit), plus use more energy to dramatically shift temps in a short period of time. If renting, you might not care about the AC unit. And for some, the power bill is part of the rent. But if you own, pay a monthly bill or want to be "green" it's a smart move to keep temps within a gradual range.

Think of it this way... when you boil a pot of water it takes a good bit of time and energy to get it going. If you're not quite ready to use the boiling water, you only have to turn down the temp. a fraction. And it only takes a fractional change to get it going again. But if you turn it off and let it go stone cold, it'll take another chunk of energy to get it going again.

So let the AC unit maintain an o.k. temp. It might only kick on a few times a day if set above 80, so your costs will be minimal. But if you want it to turn a whole place from 90 to 75 within an hour or two from coming home from work, it'll be cranking full blast for a good spell.

[budaboo]

What about people that leave for weeks at a time during the summer? Is it best to leave the a/c on at a higher setting or just turn it off? I'm not sure what the extreme heat would do to a house if anything.

[aiwei]

I think you should leave the ac on even if you are leaving for days or weeks at a time in the summer. Set it at a minimum temp, 85 to even 90 degrees. It will keep indoor temp and humidity even while you are gone.

[azjack]

"What about people that leave for weeks at a time during the summer? Is it best to leave the a/c on at a higher setting or just turn it off? "

I was recently travelling for 2 1/2 weeks, and I left the a/c unit on, but turned way up to 94. It was hot and stuffy when I returned, but the electric bill should be more reasonable.

Day to day, I set it at 88 when leaving for the day. If one has pets, that might be too high. When I am home, I set it as low as necessary for comfort.

Maybe someday I will get one of those large complicated digital thermostats where you can set temps in various zones hour by hour and day by day. They look like something from the Starship Enterprise.

[amatrine]

We have pets. when they are home alone we leave it at 80.

[Ponderosa]

I've always heard "let it run all day." But, I was watching the news a couple nights back and there was a piece on how the weather guy paid only $76 for his electric last month. The trick? He just turned off the a/c everyday from 9 am to 9 pm, his time of day rate boundaries. That really caught my attention and it is a massive savings.

As for what happens when you turn off ac all day, my only experience is from a power outage we had last year early on a 115+ day. It warmed to mid-90s in the house by the time the power came on (around 6:30 pm) but it quickly cooled down to comfortable levels.

I don't think I would want to do this if at home, but APS peaks are noon to 7pm, and that would be reasonable for most people's schedules. On weekends, of course it's all off-peak.

[wit-nit]

We tried that turn off during the day experiment a few years ago and found it made very little difference as the A/C had to run longer and harder to make up the difference when we came home in the evening.
We did discover that it played havoc on drying out the furniture and the creaking walls that were probably warping to some degree by expansion/contraction. Also the musty smell was not so good either. And some foods turned bad too. They get hot and dryout or ?? in the cupboards.

[aiwei]

There were a few days I kept our ac off all day. The house was around 95 degrees or hotter. Then I noticed the refrigerator ran constantly during those days. To make matters worse, if your fridge/freezer is like mine which the doors sometimes do not close all the way, your food might start to warm up or thaw too (mine did!)

Now i keep our ac on at a higher temp (85-87) all day and my last bill was $216, which was not too bad.