How to chill with efficient a.c. in heat wave

Horrible heat! Across the country, 132 million Americans are suffering heat advisory conditions. What to do to beat the heat? First, give yourself a break! Take it easy; it's important not to exert yourself, as our cat, aptly named Penguin, demonstrates on a cool tile floor. Second, don't make your air conditioner overexert. For efficiency's (and your budget's) sake, turn it off when you leave for more than a couple hours, and, if you leave the a.c. running, turn it up to at least 80 degrees until you come back. Pull shades and curtains, too, to keep out solar heat. When it's a record-breaking hundred-plus, 80 indoors is sweet relief, and you can always turn down the thermostat when you return.

But don't turn it down too far! The more power we burn, the more greenhouse gases we contribute to global warming, not to mention brown-outs and no a.c. for anyone. Plus, cooling is responsible for 17-22 percent of the average residential electricity bill . Every degree you go above 72 increases your savings by one to three percent, says the California Energy Commission. And, with every degree you lower it, cooling costs increase by about 7 percent. As Mayor Bloomberg, ever the cool head, advised New Yorkers this morning, keep your a.c. at about 79 degrees, the most efficient setting that still feels cool.

If you've got a programmable thermostat, set it to turn the a.c. on half an hour before you get home.

For more a.c. info, see my "Econundrums" column in the August issue of Whole Living Magazine, and this helpful summer energy slide show at wholeliving.com.

Please visit my home page at GreenerPenny.com for tips on green, nontoxic sunscreens and cosmetics, updates on the toxic plastic chemical BPA in drink bottle linings, and info on my book, Do One Green Thing. Sign up for my free monthly e-newsletter, and don't forget to ask me questions or comment on this blog!