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Saving Energy By Degrees

If your home has central heating and air conditioning, you probably use a wall-mounted thermostat to control the temperature. A manual thermostat must be adjusted by hand each time you want to make your home warmer or cooler.

Programmable thermostats let you preset temperatures for different times of day. That way, your home’s occupants can remain comfortable when they’re present and active, and you can save on heating and cooling costs when they’re absent or asleep.

Either type of thermostat should go on an interior wall away from vents or other sources of hot or cold air.

Programmable models pay for themselves quickly
A programmable thermostat costs more than a manual model, but you will quickly recoup the extra cost. The federal government estimates that a homeowner in Louisville can save as much as $200 a year by using a programmable thermostat rather than a manual model. That’s more than tenfold the estimated $19 price difference between some manual and programmable models.

Those savings assume optimal use of your programmable thermostat. They also assume your home has a furnace or boiler for heating and a separate system for air conditioning.

The federal ENERGY STAR program recommends baseline settings of 70 degrees or lower in the winter and 78 degrees or higher in the summer. Those should be your settings for the hours you’re awake and at home.

For hours when you’re out of the house, ENERGY STAR recommends settings at least 8 degrees cooler than the baseline in the winter and at least 7 degrees warmer in the summer. For hours of sleep, the recommended values are at least 8 degrees cooler in the winter and at least 4 degrees warmer in the summer.

In the winter, each degree you set back your thermostat at night should shave about 1 percent from your annual heating bill.

The ENERGY STAR Web site ( includes a calculator that estimates energy savings from using a manual or programmable thermostat. Homeowners can enter their fuel and thermostat costs, type of furnace or boiler, target temperatures, and usage pattern. Results can be calculated for dozens of cities.

Settings are different with heat pumps
There is an exception to the rule that homeowners with separate heating and cooling systems can save money with programmable thermostats. That exception is the heat pump—a unified system that both heats and cools.

When a heat pump is working like an air conditioner, a thermostat can save energy and money. But when a heat pump is pulling heat from the outside air or ground and using it to warm a home, it’s cheaper to maintain a moderate temperature setting.

Some companies sell programmable thermostats designed for use with heat pumps.

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