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Leave A/C on during day?

W

WhiteKnight

Platinum Member
I read somewhere that it's more efficient to leave your air conditioner on all day even if you are not there than it is to turn it on when you get home, forcing the recooling of your whole home. Can anyone speak to the validity of that? It's in the 90s here in Baltimore and I've been leaving my AC on low when I go to work every day but I'm wondering if that's the best choice.
 
If you're asking efficiency, it certainly isn't efficient to do it between the hours of 2-8pm.
 
I don't think that makes much sense, at least as far as your electricity bill goes.. It shouldn't take very long for your A/C to cool your house down, assuming it's the proper size.. the extra hour or whatever it takes to lower the temperature to the point that the A/C shuts off will be insignificant compared to the power the A/C uses cycling on and off all day.

Of course, I could be wrong.. It's 5:35am.
 
True.

Remember, you do not have to just cool air, but the furnature etc. That makes the compressor run constantly even in the night. Better to let it run and make sure lights etc are out. Try to keep the heat produced in your home to a minimum
 
my roommate and i experimented, and it stays cooler if we leave it at like 76-77 then to turn it off, and have to cool it way down when we get home from work. and, our power bill hasn't changed, soo...it works for us.
 
Well, I guess I'll just keep leaving it on low all the time then. It doesn't bother me to wait while it cools down if I were to turn it off while I'm at work, but if it's going to cost me the same amount anyway, I guess I might as well just leave it.
 
turning AC OFF when leaving the house is just SILLY.

leaving it on auto and raising the temp a bit makes sense.

we leave our A/C at 77 when we're home and 80 when we're away.
 
Over the last 2 nights, we've had a chance to use our CAC. It gets to be 90F on the 2nd floor while the 1st floor stays at a cool 75F because of the tiled floors.

Right before bed, we poppped on the CAC (only 1 zone so it regrettably does both floors) and it cools down the upstairs in less the 30 minutes. After that short amount of time, we're good to go as far as comfort is concerned so I go back downstairs to turn it off. We could easily fall asleep thereafter.

I think the ambient temperature is the biggest concern, but I wouldn't go to the lengths of leaving it on all day as opposed to just cooling down the place in one shot in a span of 30-60 minutes.
 
Basically, you'll save energy if you turn it off. There are those who believe running the A/C for 8 hours a day is more efficient than trying to cool down the house/apt after you get home from work. Depending on where you live, you might even be able to open some windows and cool your dwelling that way. I live on the second floor of an apartment complex that's on a hill...I can cool it down to around 78 degrees or so with just the windows open, but my roomy doesn't understand the value of the dollar and he leaves the A/C on because he never shows up to work until after 10am or 11am.....(loser) If you're in a house, check into your roof vent systems and make sure your house cools properly without A/C....that will definitely make a diff when you're trying to cool down the rest of the house. I recommend Ridgevents if you don't have them. They're pretty good.

-Scar
 
Originally posted by: Scarpozzi
Basically, you'll save energy if you turn it off. There are those who believe running the A/C for 8 hours a day is more efficient than trying to cool down the house/apt after you get home from work. Depending on where you live, you might even be able to open some windows and cool your dwelling that way. I live on the second floor of an apartment complex that's on a hill...I can cool it down to around 78 degrees or so with just the windows open, but my roomy doesn't understand the value of the dollar and he leaves the A/C on because he never shows up to work until after 10am or 11am.....(loser) If you're in a house, check into your roof vent systems and make sure your house cools properly without A/C....that will definitely make a diff when you're trying to cool down the rest of the house. I recommend Ridgevents if you don't have them. They're pretty good.

-Scar
Click to expand...

do you turn off your water heater everytime you leave the house?

i still think it is better to leave your ac at a moderate temp when out of the house than turning it off altogether.
 
I live in an apartment with west facing windows so if I turn the AC off during the day in the summer and come home from work at 5:30 or so the apartment will usually be around 95%, even with all of the shades drawn. Because of that, I've been experimenting with leaving the AC on during the day and it's been a lot more comfortable. We'll see the verdict when my power bill arrives. We're in the middle of a heat wave right now. Usually if the outside temp is 75 or lower I'll just use the windows and a fan.
 
It is more efficient to reduce your HVAC use when you are not around than to leave it on constantly. The linked article refers to heating via a furnace, but the principle also applies for air conditioning.

If you have central air, installing a programmable thermostat is best. You can turn down your HVAC system right as you go to sleep, have it turn back up before you wake up, turn it off as you leave, and turn it back on before you get home. A good one costs between $50 to $100, and, depending on the size of your home, you can easily realize that in energy savings in the first year. Assuming that your home is appropriately weatherproofed.
 
mmm.... I love A/C

I can't handle uber heat

my A/C goes up during the day (not off though), and temp comes back down 30 mins before we leave work. 😀
 
Running your A/C would drive your power bill through the roof. I generally turn it on for a little while when I get home, to cool the house down. After I turn it off, we have a couple of fans that we use to keep cool. A ceiling fan also helps circulate air and cool things down a little and it's a LOT cheaper to run your ceiling fans constantly than it is to run the A/C all the time.
 
Originally posted by: Encryptic
Running your A/C would drive your power bill through the roof. I generally turn it on for a little while when I get home, to cool the house down. After I turn it off, we have a couple of fans that we use to keep cool. A ceiling fan also helps circulate air and cool things down a little and it's a LOT cheaper to run your ceiling fans constantly than it is to run the A/C all the time.
Click to expand...

I think the arguement here is that running the AC all the time will allow the compressor to be off most of the time so the unit is essentially acting just like a fan. Turning it on when you get home forces the compressor to run for an hour or whatever straight. That's by far when it draws the most power.
 
Originally posted by: Encryptic
Running your A/C would drive your power bill through the roof. I generally turn it on for a little while when I get home, to cool the house down. After I turn it off, we have a couple of fans that we use to keep cool. A ceiling fan also helps circulate air and cool things down a little and it's a LOT cheaper to run your ceiling fans constantly than it is to run the A/C all the time.
Click to expand...

Actually, my family had tried turning our AC off during the afternoon, and out power bill actually went up (due to having to cool everything in the house to 70 degrees from almost 90). Out AC unit comes on for about 10-15 minutes every hour. After trying the "turn it off when you're not there" method, the AC unit would have to run almost constantly for two hours when we got home. Thus negating the cost of the electricity saved through the afternoon.

And with ceiling fans - it depends on how many you have.
 
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