A thermostat controls a heating (and cooling) system, turning it on and off to maintain the set-point temperature; larger buildings have multiple zones with separate thermostats. With heating, the lower the setting, the less heat is called for and the less energy will be used. A common rule of thumb is that for every degree Fahrenheit you turn down the thermostat, you save about 2% on heating costs. So, if you normally keep a house at 70° and drop the setting to 65°, you’ll reduce heating costs by about 10% (5 x 2%).
If you lower the thermostat for a portion of each 24-hour day during the heating season, say at night, there will be proportional savings. For example, if your thermostat is set to reduce your house temperature by 10° for eight hours each night (one-third of the 24-hour day), your annual savings would be about 7% (10 x 2% ÷ 3).
Published October 30, 2009