The recommended winter setting for a home thermostat when people are at home is 68 degrees Fahrenheit (20 degrees Celsius). If you keep yours above that, reduce it to 68. Once you've gotten used to that daytime temperature (or if you already had it set there), try setting it a few degrees lower. You'll have to experiment to see how low you can stand it -- you don't want to blow the money you saved on heat buying mittens. The exact amount you'll save varies based on heating prices, the size and efficiency of your house and the temperature outside. A rough estimate: 1 to 3 percent savings per degree of thermostat setback [sources: U.S. Dept. of Energy and Madison Gas & Electric].
To save even more, crank the temperature down to 60 or 55 degrees Fahrenheit (15.6 or 12.8 degrees Celsius) when you're away or in bed. (Some people even go down to 50, or 10 degrees Celsius.). If you work outside the home during the day and sleep eight hours a night, you'll be reducing your energy usage for 16 hours per day. If you turn the heat down from 68 degrees to 55 degrees, you'll save 26 percent on your heating bill [source: Madison Gas & Electric]. That will translate to hundreds of dollars in savings in just a year or two. If you're home during the day and need the heat, you'll save about half as much by just turning it down at night, which is still a nice savings.
By the way, it's a common myth that you'll use so much energy getting the house warm again that you won't save anything by turning it down. When you turn the heat down, the heat doesn't run as the house's temperature falls. You save enough energy then to counteract the energy used to reheat the house, so you break even. The savings come during the time you leave the temperature down, since the heating system isn't working as hard to maintain a differential between the inside and outside temperatures. The longer you leave the thermostat turned down, the more you'll save.