Use a programmable thermostat to keep cooling costs in check

To prevent your utility bills from rising along with the mercury, consider installing a programmable thermostat or learning how to use the one you have now. By tailoring your air conditioning (or heating) to your schedule, programmable thermostats can save both energy and money, but only when set correctly. Setting it incorrectly can actually cost you more. Here's how to choose a programmable thermometer and maximize its benefits.

There are three types of programmable thermostats. To decide which one is best for you, think about your schedule and how often you are regularly away from home for extended periods of time. The government's Energy Star program suggests the following:

• 7-day models are best if your schedule tends to change day to day. They offer the most flexibility, and let you set different programs for each day—usually with four possible temperature periods per day.
  
• 5+2-day models use the same schedule every weekday, and another schedule for weekends.
  
• 5-1-1 models are best if you tend to keep one schedule Monday through Friday and have different schedules on Saturday and Sunday.
  

Some of the programmable thermostats tested by Consumer Reports in the past have been tricky to use. We are testing another batch now and will have the results later this summer. Energy Star has encouraged manufacturers to simplify set-up. Typically, a thermostat comes with four pre-programmed settings. Just sticking with those settings will result in significant savings but they may not match your schedule. Many models also come with such additional features as digital, backlit displays; touch pad, voice and/or phone programming; hold/vacation settings; indicators that tell you when it's time to change air filters or signal that your system is malfunctioning, and recovery features that remember your last settings in the event of a blackout.

Only you can determine what setting gives you the most comfort. But, on average, every degree you raise your thermostat in the summer or lower it in the winter, saves two percent on your energy bill. To get the most from your thermostat follow these tips from Energy Star:

• Install your thermostat away from heating or cooling vents or registers, heat-generating appliances or electronics, open doorways and direct sunlight.
  
• When programming the thermostat, keep it set at a constant temperature for long periods of time, such as eight hours at night when you're sleeping and the same period during the day when you're at work.
  
• When on vacation, set the hold button at a constant temperature.
  
• Resist the urge to override your settings. Every time you do that, it costs you money.
  
• If your home has zoned heating and cooling, install a programmable thermostat in each zone, especially if parts of the house, like a college student's bedroom, are unoccupied for long periods of time.
  
• If your thermostat runs on batteries, change them at least once a year.

But if all this seems like too much work and you want to stick with your manual thermostat, you can still realize savings by adjusting the temperature 5 to 8 degrees (up in summer, down in winter) when you leave in the morning.

—Mary H.J. Farrell