Thermostats measure your home's ambient temperature and use that information to activate your furnace or your air conditioner, depending on the thermostat's setting.
A mechanical thermostat works when its bi-metal coil contracts and expands with the room temperature. The movement of this coil activates a switch that opens or closes a circuit to make the furnace, heat pump, or air conditioner turn on and off.
Programmable electronic thermostats make it possible to automate the way your thermostat works and use your home climate systems more efficiently, resulting in lower energy bills. Their timers allow you to warm up your house before you get out of bed in the morning or come home after work and can be set at different temperatures for different times of the day. If you have a mechanical thermostat, you might consider switching to a programmable electronic model. Look for thermostats that allow you to program daily cycles, weekly schedules, and override default settings.
Sophisticated zone-controlled home climate systems divide the house into several separate zones or areas that may each be controlled by separate settings and times on a individual thermostats. With zone controls, thermostats open and close dampers, sending warm or cool air when and where needed.