You can save as much as 10% a year on heating and cooling by simply turning your thermostat back 7°-10°F for 8 hours a day from its normal setting. (If you have a heat pump, don't do this without a programmable thermostat). You can do this automatically by using a programmable thermostat and scheduling the times you turn on the heating or air conditioning. As a result, the equipment doesn't operate as much when you are asleep or not at home.
Programmable thermostats can store multiple daily settings (six or more temperature settings a day) that you can manually override without affecting the rest of the daily or weekly program.