What makes the heat pump so efficient is the way it operates. Instead of burning costly fuels such as propane or oil, the heat pump moves heat without a flame. It does this by extracting available heat from the outside air and transferring or ''pumping'' it inside your home. During the summer the heat pump reverses this operation extracting heat from the air inside your home and pumping it outside.

The way the heat pump operates can be explained without getting too technical. Two basic physical principles are at work in the heat pump:

• Movement of heat from a hot object to a cool object.
• A pressurized gas allowed to expand becomes cool.

To achieve year round comfort, the heat pump uses the same basic components as the refrigerator: Coils to carry refrigerant gas, a compressor to increase the pressure of the gas, and fans to circulate air.

During the winter a fan pulls air over the outdoor coil which extracts heat from the outside air. Even though winter air feels cold to us, it holds a great deal of heat. The compressors pressurize the gas in the coil, raising the temperature even higher. The heated gas moves inside your home to the indoor coil. A circulating fan blows air across the indoor coil and through heating ducts, the heat is drawn from the gas in the indoor coil and transferred to the air in the ducts.

During the summer this process is reversed automatically by a valve or switch on the heat pump.

Like any other machine, the heat pump will perform best if it is properly maintained.