I will confess a bias here. I love warm weather, even when it slouches toward humidity. I detest the harsh, slightly metallic quality of the air forced through even the fanciest AC systems. The only air conditioner I own sits, unused, in my car; my home is happily unrefrigerated. But given the energy mess we're in, I can now gild my personal preference with a patina of high-mindedness: air-conditioning is bad for the planet, and for national security, and for our balance-of-payments deficit. Unfortunately, it is not as bad as I'd like it to be - in part because not all of our electricity is provided by fossil fuels (although coal does predominate). And also because air-conditioning represents a relatively small slice of our energy use, an estimated 4%.