Is it better to leave my home air conditioner on all day at a constant temperature or to vary the temperature?

Question

I had a new thermostat installed and it allows me to set several different time blocks during the day to specific temperatures. As an example, I can have the house at 72 degrees from 6 am to 9 am and then at 85 degrees from 9 am to 5 pm and then back at 72 from 5pm to 12 pm and so on. My fiance thinks that it is more energy effecient to leave the house at a constant temperature all day so the the air conditioner does not have to work as hard to cool down the house between temperature changes. I think it is a waste to cool the house all day long when we are not at home, and that "recooling" the house once in the evening takes less energy than maintaining the same temperature all day. Any thoughts on who is right?

Answer 1

there are lots of websites that say the same thing, use the thermostat like it is made, to save energy all day when noone is home. here is what Con-Ed has to say about it:

http://www.coned.com/customercentral/energysavingtips.asp

Don't cool rooms that aren't occupied.
Open windows on breezy days instead of turning the air conditioner on.
Make sure your air conditioner is the proper size for the area you are cooling.
Check your air conditioner filter at least once a month and keep it clean.
Turn off your air conditioner when no one is home.
Set the automatic timer to turn on your air conditioner 30 minutes before you arrive home.
Ceiling fans can make your air conditioner's job easier while saving you money.
A two-degree adjustment to your thermostat setting (higher in summer, lower in winter) can lower cooling/heating bills by four percent and prevent 500 pounds of carbon dioxide from entering the atmosphere each year.
If installing a new central air conditioner (or heat pump), you should know that recent field studies suggest that approximately 75 percent of installed cooling equipment may have incorrect amount of refrigerant. An incorrect refrigerant level can lower efficiency by five to 20 percent, and can cause the equipment to fail prematurely

Answer 2

If you are going to be gone all day, it makes sense to drop it down a few degrees. A) while the house is cooler, less heat is being lost. and B) perhaps the sun will warm things up for when you get home later in the day, and so it won't take the fuel it would have to maintain the warmth during the cool hours of the morning. This is most obvious in central florida, where you might well be able to leave the heat off most days, as you don't need much at night while you sleep, and only get up in the morning to leave, and in the afternoon it is usually reasonably nice.

Answer 3

People trained in this field agree. Air conditioners are designed to lower the outside air by about 10 degrees. Greater differences in temperature strain the machine and increase costs enormously. Use your AC when you are in the house but no lower than to 73 degrees. When you are not in the house allow the house to rise to 80 degrees. On your way home start the cooling down time to 73 degrees until bedtime then allow the AC to rest until mid morning and start over.

Answer 4

From what my own air-conditioning man told me, you should leave it at a constant during the day, and reset for 80 degrees at bedtime. Reasoning is, once house is cooled to desired level, it takes less energy to maintain that level than to allow it to heat up and then have to cool down again from higher settings when you are going to be gone during the day. If you are going to be away for several days, you could raise to about 85 degrees and still maintain a head start for cooling down when you get home. if your house is well insulated, you'll find your system will cycle less using this approach, and your electric costs will be minimized. At 85 degrees, it would probably not run at all during the night. Another tip to save on your energy bill: I set my thermostat at 77 degrees because we use small fans & ceiling fans to keep air moving, thus requiring less cooling of the static air in the house. We stay quite comfortable using this approach.

Answer 5

I think it would be allot cheaper to leave it off when you are away(unless you have pets) and have it kick on an hour before you get home. Your air conditioner is a pump that pumps hot air out, so pumping air out all day is a waste of electricity and money. Remember to close the shades and curtains while you are away and your house will stay cool because nobody is going in and out of the door to let the heat in. Your plants may like it alittle warmer anyways. Let him know you are saving money to buy something nice for the both of you.

Answer 6

it takes more energy to cool down, then to maintain a constant temp. I set mine during the hot part of summer, to kick on about 10am and lower the temp to 72 degrees. Then at about 4pm, it drops to 70 degrees. then at 10pm it goes back up to 74. that way, it cools the house to a slightly warm but comfy temp while most people are out of the house, cools it to a nice temp about the time we get home, and then goes off during the cooler part of the night. My electric bll drops by over $100.00 dollars this way, as opposed to either running all day to stay at one temp. or having to come on and cool a very hot house down for the afternoon.

Answer 7

I've heard to save engery you set your thermostat to 72 then turn it up to 75 when you arn't home. For every two degress higher you turn it you save energy.