In colder parts of the country, heating accounts for 36 percent or more of annual energy bills. Depending on where you live, reducing the amount of energy used for heating may be your most effective way to lower your home's energy bills.

Heating systems basically replace heat that is lost through your home's shell (see the section, Your home’s exterior). They accomplish this by converting a fuel into heat that is transferred to the air of the living space.

How much energy your heating system requires to replace that heat depends on four factors:

  1. The climate where the house is located
  2. The home's size
  3. How energy-efficient the house is
  4. How energy-efficient the heating system is

You can't do much about the first two factors. Climate and size are not easily changed. However, you can do something about the last two, improving the energy efficiency of the home itself and specifically, its heating system.

There are a variety of heating systems and combinations of systems used in homes. They can be classified either by the type of fuel used or by the mechanism used to distribute the heat throughout the home.

Central heating systems have three basic parts: the heating plant where fuel is converted into heat, a distribution system for delivering heat to where it is needed, and controls to regulate when it operates.