I don’t normally look forward to Mondays, but yesterday I sure was glad to go to work. As much as I enjoy my job, what really put a smile on my face was that after a pricey weekend of air-conditioning, I could switch off the A/C at home—someone else would foot the cooling bill during the workday.

The New York City metro area, like much of the country, is in the midst of a heat wave. Based on the extreme temperatures throughout the U.S., I’m likely not alone in appreciating the cool comfort of the office.

Of course, returning to a sweltering home isn’t much to look forward to, so before I left for work yesterday I pulled down all the window shades to keep rooms from heating up too much. (A side benefit: The air conditioner wouldn’t have to work so hard or run as long to cool the house in the evening.) And I turned off all the lights. For more tips on decreasing how much you run your air conditioner, see “How to keep your cool.” And read “Cool runnings” to learn how to maintain your A/C and lower your utility bill.

If your air conditioner is more than eight years old, you might want to consider replacing it. New units are lighter, quieter, and about 25 percent more energy efficient than older models. “Quiet comfort,” our latest report on room air conditioners, covers the essential features, and our exclusive sizing worksheet will help you figure out what capacity unit is best for your home. Then use our Ratings (available to subscribers) to find the right model.

No matter where you spend your days during a heat wave, drink plenty of water and wear comfortable clothing. If you’ll be spending time outside, apply sunscreen and follow our safety tips to avoid health problems.—Celia Kuperszmid Lehrman

Essential information: Find out which insect repellents work best (Ratings are available to subscribers).