Being married to Matt, the Saver of All Things Environmental, makes me feel guilty about having a house with central air. Unlike a lot of people with air conditioning, we do not turn our air on when it first gets hot and leave it on till the leaves start changing color. Seriously--our neighbor in our old house ran her air from May till October, even though the nights on Long Island are often in the mid to high 50's even in July and August!
We take a much lighter take on using the air. On the days it's hot enough to warrant it (and here we are at the end of July, and I think we've only used it 10 or 12 days so far) we leave the windows open until it's uncomfortable. Then we seal up all the windows and put it on at 70 degrees. After it's cooled to that, we nudge it up to 72 or even 74. Then we watch the conditions. If the heat dissipates at night, off it goes and the windows are opened after the chill is gone. If we're going to leave it on for another day, we make sure it won't be too cool for the night. Then when Matt gets up early for work, he puts it down again, to cool it off using the least energy (when it's coolest outside) and I turn it back to 72-74 when I get up.
Having said that, when the days and nights are hot and humid--it's been going in cycles this summer, with a week of stunningly perfect weather, then a few icky humid days, then maybe a day or two of rain, then back to perfect--I am happy to be an energy-hogging American with a cool, comfortable house!
Which I guess, you could argue, is the problem with being an American!!!!