As well as the options in place to deal with changes in weather. Having no a/c in Hawaii is possible (and probably environmentally better), but it can really be miserable at times. And even dangerous to health, if we're talking about babies or the elderly.

I don't run my a/c during the day, but I need it to be cool to sleep comfortably. (Of course, my idea of "cool" is 74F/23C. )