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# Does it cost more

to leave the a/c on all day or to cut it off during the cool hours of the day?
I am just trying to figure out if it will cost more on my electric bill to only have my a/c on from say 1pm-8pm or leave it on all day on the same temp.

Asked by mrsbean08 at 8:43 AM on May. 29, 2010 in Home & Garden

Level 17 (3,629 Credits)
• depends on where you live & how hot your house gets. if the ac is having to work really hard to cool the room from like 95 down to 65 then its better to leave it on all day. if your house gets warm in the afternoon cuz of the sun but doesn't really heat up in the am then just switch it on when you need it.

Answer by Nyx7 at 8:48 AM on May. 29, 2010

• It will cost more if you turn off the central air during the hottest part of the day, and turn it back on when you're home. Reason being, if your home heats up inside, it will take that much more energy (cost) to lower the inside temperature from say 86+ to a comfortable 68-72 degrees (in the summer). Whereas if you set your thermostat for say 70 degrees (average), and "allow" the temperature to rise to say 78 degrees, when the AC turns on, it will only have to work to lower the temperature 8 degrees as opposed to 16 or more (using my numbers as examples).

It's more cost efficient to maintain a specific range than to turn systems on an off regularly. My MIL does that, and always complains that her electric bill is 3-4 times what we pay--and our home is 3 times larger by square footage than hers! :o)

Answer by LoriKeet at 8:50 AM on May. 29, 2010

• It will cost you MORE to run it ALL day. The whole idea that it will take more energy to cool down the house that has had no AC all day is a myth. The LESS you use the AC the lower your bills WILL be. This is because you are using LESS energy.

Answer by SAHMinIL2 at 8:58 AM on May. 29, 2010

• I leave the AC on when we're not here, but use my programmable thermostats to turn the temp up a few degrees. I keep it generally around 74-75 when we're here, and set it about 77 when we're not. That way, we don't have a drastic cooldown needed when we get home, but with the higher setting, the AC shouldn't have to run quite as much when we're not.

Answer by vicesix at 9:03 AM on May. 29, 2010

• Also older homes in general cost more to heat or cool because they are "leaky" compare to newer homes. Where the thermostats is set is also a big part into the cost. They Higher the thermostat is in the summer the lower the bills are. The lower the thermostat in the winter the lower your bills are. Our central Air Unit broke two summers ago. So we have been going without and living just fine. Although when we did run our AC we had the thermostat set to 78. Our home 78 in the summer (when we ran our AC [central air]; 72 in the winter.

Answer by SAHMinIL2 at 9:04 AM on May. 29, 2010

• Why not just get an electronic programmable thermostat so that you can program the a/c to cool your home to specific temps at specific times? This will save you on energy costs because the a/c will be able to kick on & off automatically, keeping your house from getting too hot & forcing the a/c to work twice as hard to cool your house down when you do want it running, yet at the same time saving you money by not having to leave the a/c on all the time to keep the house really cool when you're not even there.

Answer by Anonymous at 3:48 PM on May. 29, 2010

• I hear it is cheaper to keep it at the same temp all the time