Turn the thermostat back 7-10°F for 8 hours a day
Added
DOE's Energy Saver guide says setting your thermostat back while you're asleep or away saves energy. If you have a heat pump, the guide warns not to do this blindly, so check how your system recovers first. A programmable or smart thermostat can run the schedule for you.
The result
Result: DOE: as much as 10% a year on heating and cooling by turning the thermostat down 7-10°F for 8 hours a day in fall and winter.
Source
US Department of Energy, Energy Saver guide (PDF) (opens the original source in a new tab). Check it for the latest numbers before you act.