Metateps

If you have a central heating system, check the filters and clean or change them before they get dirty. In cold months keep your thermostat at the lowest temperature you are comfortable with (say, 68 degrees F in the daytime and 60 degrees overnight). Open curtains and blinds on sun-facing windows, but at night keep blinds and curtains closed to keep the warmth inside. Place pans of water near radiator tops and warm vents, or run a room humidifier. Moist air makes you feel warmer than dry air.

Have an HVAC professional check your heating system every couple of years.

For various reasons you should be sure to use an air conditioner that's the proper size for the area you're cooling. Too large, and the unit will turn off and on frequently. Too small, and it will run all day, and probably all night because it didn't get the area to a comfortable temperature before bedtime.

Locate your air conditioner on the shaded side of the house. An air conditioner in direct sunlight will use more energy than one running in the shade. Closing the fresh-air intake on hot days will save some energy, as the precooled air indoors is recirculated. Close off rooms that don't need to be cooled. If you're going to be out all day, consider putting your AC on a timer so it's off all day but will cool your home just before you get home.

In hot months keep the thermostat set as high as you can comfortably stand it (say, 78 degrees). Fans can help, circulating air and allowing you to keep the thermostat somewhat higher, and sometimes eliminating the need to run the air conditioner. Even large ceiling fans use only a small fraction of the electricity required to run an air conditioner.

When it's hot, avoid doing anything that would increase the humidity, like cooking, showering, or washing clothes. Do those tasks in the early morning or late evening when it's cooler. Also, ovens and other heat-generating appliances should be used only in the early morning or late evening.

Check your AC filter monthly and replace or clean it if it's dirty. Keep the condenser coils and fins clean (see the owner's manual for instructions).