This article explains how to choose a home thermostat, remove your old thermostat, and install a new programmable home thermostat. According to energystar.gov, “The average household spends more than $2,000 a year on energy bills — nearly half of which goes to heating and cooling. Homeowners can save about $180 a year by properly setting their programmable thermostats and maintaining those settings.”

How does the system work?

Air conditioners employ the same operating principles and basic components as your home refrigerator. Refrigerators use energy (usually electricity) to transfer heat from the cool interior of the refrigerator to the relatively warm surroundings of your home; likewise, an air conditioner uses energy to transfer heat from the interior of your home to the relatively warm outside environment.

An air conditioner cools your home with a cold indoor coil called the evaporator. The condenser, a hot outdoor coil, releases the collected heat outside. The evaporator and condenser coils are serpentine tubing surrounded by aluminum fins. This tubing is usually made of copper.

Air distribution system ducts are designed to supply conditioned air from space heating and cooling equipment to the living spaces and return an equal volume of air from the living spaces back to the heating and cooling equipment to be conditioned. Ducts are usually located in unconditioned spaces such as attics, crawlspaces, garages, or unfinished basements and made out of thin materials that easily conduct heat.

Due to the extreme winter and summer temperatures in these spaces, 10 percent to 30 percent of the energy used to heat and cool the air is lost to conduction through the duct surfaces. In order to maintain temperatures at a comfortable level, the heating and air conditioning equipment has to compensate for this heat loss or gain by conditioning additional air. Thus, uninsulated or poorly insulated ducts reduce the efficiency of the heating and cooling systems and increase energy bills.

Energy is being lost unnecessarily in homes through heating and air-conditioning duct leaks resulting from deterioration or improper installation. By correcting these problems you can save tremendous energy losses.

You can see in the image to the right, the ductwork is leaking heat around the joints into the unconditioned basement of this 1979 home. Ducts that pass through unconditioned spaces, attics, garages, or crawl spaces, have a good chance of losing energy. Losses can be very high if the ducts are uninsulated. Even when the ducts are wrapped with insulation, leaks at joints and corners can be big energy losers. Leaks in supply ducts lose heated or cooled (conditioned) air to the attic or crawl space or between floors before the air can be delivered inside the house, wasting energy.