The temperature in most houses is controlled by a mechanical thermostat, which keeps the temperature constant around the clock. Many homes are unoccupied for many hours and when we sleep we don't need as high a temperature as when we are up and around. An electronic programmable thermostat allows us to save energy, all year, by adjusting the inside temperature when we don't need our preferred level. For each time zone, thedesired temperature can be specified. The thermostat also has a special setup for weekends and a manual override of the program for special occasions.
Programming is simple to do, using a few buttons on the panel.
It took me about 20 minutes to install my device, including removing the old mechanical thermostat. Before throwing away the old thermostat, check if it uses a small glass capsule with mercury in it. It is best if it could be safely deposited, since mercury is a hazardous material. However, the jewelry department at Kmart has started to recycle mercury batteries, they were nice and took my capsule as well. Once in awhile there are also community collections of hazardous wastes from households.