How do you use central a/c efficiently?

My husband and I are from the city where air conditioners are indiv units installed in wall of specific room. When we want the a/c on, we turn it on. When its cool enough or when we go out for the day we shut it down.


I know we are not supposed to do this with central a/c but my husband insists when we go out for several hrs we turn the central a/c off. When we do that, we come back to a very hot house and then we turn the A/C back on and wait until it clears the hot air. I think this wastes energy, my husband thinks we are saving. We have 2 zone A/C. One zone for upstairs bedrooms and one zone for downstairs main floor. Also how should we set the thermostats for the zones. We have 2 return ducts for the whole house located on second floor stairwell(center of house). Thanks.

How do you use central a/c efficiently?
You need to leave them on! Set your zones to be cooler when you will be there.





At night until 8 am my upstairs is set lower than the downstairs. If my sons are gone (several days at a time and it happens frequently) I turn off the upsatirs AC and just use a window unit in my room.





During the day when we are home its the opposite. The temp you choose is highly personal.
Reply:There are many factors that influence the decision to leave the a/c on or turn it off. Depends on how good your insulation is, draftiness of house, desired inside temp, current outdoor temp, etc.





I might bump up the temp setting a few degrees when going out, but I wouldn't turn it off, in general. I does take a long time to recool the whole house.
Reply:is your a/c a heat pump? that is the most efficient a/c. what you need are digital/ programable thermostats. set the thermo for the bed rooms to kick on about an hour before you go to bed, and set them to maintain an "away" temp of about 80 in the summer and about 65 in the winter. as for the living room/kitchen area, set it to turn on about an hour before everyone wakes up, an hour before the kids come home from school, etc. also, have everything set to turn off approx. an hour before you leave, it will take a while for the rooms to heat up or cool down and you'll be gone before it gets uncomfortable. but tell your husband that to turn everything completely off and the to have to cool down and entire room from scratch is very inefficient. talk to you electric company, they will give you lots of good tips.


if you have an attick or crawl space, they make fans that go in the vents at the end of your house or in the whirly bird vents on your roof that kick on at about 100 degrees. they draw the hot air out of your attic and reduce your cooling cost.


I live in oklahoma, last year we had around 65 days of 100+ degree days. we have a house that is 2800 sq feet and our electric bill has never gotten above $180.00. it also helps to have very few windows on the west wall, very good double paned insulated windows, insulation out the wazoo, bats and blown and when your building a home, sheath it in plywood or OSB. you'd be supprised the difference it makes.