Energy Star estimates that the average U.S. household spends $2,200 per year on heating and cooling bills. Further assuming a typical single-family home with a 10-hour daytime setback of 8°F in winter and set-“up” of 7°F in summer, along with an 8-hour nighttime setback of 8°F in winter and a setup of 4°F in summer, they estimate a savings of about $180 per year, or a little more than 8%.
The experts at BuildingGreen.com say that for every 1°F you turn down the thermostat, you save about 2% on heating costs. So, if you normally keep a house at 70°F and drop the setting to 65°F, you’ll reduce heating costs by about 10% (5 × 2%). If you lower the thermostat for a portion of each 24-hour day during the heating season, say at night when many people like it cool for sleeping, there will be proportional savings. For example, if your thermostat is set to reduce your house temperature by 10°F for eight hours each night (one-third of the 24-hour day), your annual savings would be about 7% (10 × 2% ÷ 3).
Although the Energy Star program no longer labels PTs, the program has good information about them and how they can save energy, if you set them up and use them properly (energystar.gov). You can also download an Excel file that will estimate your potential savings.
After you determine your estimated annual savings, divide it into the cost of buying and installing a PT to determine simple financial payback. If you are persistent and disciplined, you can buy a cheap PT and get some energy savings. But for the best savings, if you’re like the rest of America, you may want one that does the programming—and maybe also the thinking—for you.