A heat pump is one of the most energy-efficient heating and cooling systems available today. Unlike other types of heating systems which convert fuel or electricity directly to heat, a heat pump is designed to move heat from one place to another. Even at temperatures as cold as 0° F, the heat pump is able to extract some heat from outside air to use in heating your home.

A heat pump is designed to move heat from one place to another. The outdoor coil of the heat pump absorbs heat from the outside air, even at relatively low temperatures, and transfers it to your home. In hot weather the heat pump operates in reverse to provide cooling. It transfers heat from within your home to the outdoors.

The outdoor unit of a heat pump contains coils filled with refrigerant which absorb heat from the outside air. Even though the outdoor air temperature may be as low as 0° F, the refrigerant is much colder and is able to absorb heat. As it begins to absorb heat, the refrigerant evaporates, absorbing even greater quantities of heat. The heated refrigerant vapor passes through coils and then on to the compressor where it is pressurized. This process increases the temperature of the refrigerant so that it is now hotter than the inside air. The heated refrigerant travels to the indoor coil. As a fan blows air across the coils, the refrigerant condenses and releases heat which is then circulated throughout the house.

The heat pump also cools your house using the same process, but in reverse. Simply switching the heat pump from a heating mode to a cooling mode reverses the valves that control the refrigerant cycle. So instead of extracting heat from the outdoors, the heat pump will remove heat and moisture from the indoors.

Unlike other types of heating systems which convert fuel to heat, a heat pump is designed to move heat from one place to another. Even at relatively cold outdoor temperatures, a heat pump is able to extract heat from outside to heat the home. In the summer the system reverses the direction of heat movement to cool the home.

Geothermal heat pumps extract heat from the ground or from water below the surface. Because ground and ground water temperatures are typically 50° - 55° F year-round, a geothermal heat pump is not affected by outside air temperature and therefore much more efficient.

During the summer, the same refrigerant is circulated through the loop of piping and the heat pump's heat exchanger, but the heat pump's cycle is reversed. Instead of absorbing heat from the refrigerant and transferring it to the indoor air, it now absorbs heat from the indoor air and transfers it to the refrigerant, where it is given off to the ground or ground water. Because of the constant relatively cool temperature of the ground or water, the geothermal system is actually more efficient for cooling than a typical air conditioner, which must reject heat to hot outdoor air.

The geothermal system is a highly efficient and economical year-round space conditioning system. However, the heat pumps are expensive to install. In heating mode, they deliver cooler air into the house than a gas furnace.

There are two basic types of geothermal systems, open loop and closed loop. An open loop system typically uses a conventional well as its heat source. Water is pumped from the well through the heat pump's heat exchanger, where heat is extracted and transferred to a refrigerant system. The heat is then transferred to the air in the home. The water is then returned to a pond, stream, or second well. Local conditions such as quantity and quality of available water can affect the use of this type of system. Local water use and disposal regulations may also limit the use of open loop systems.

Closed loop systems circulate a heat transfer fluid (usually a water/antifreeze solution) through a system of buried plastic piping, arranged either horizontally or vertically. Horizontal loop systems draw their heat from loops of piping buried 6-8 feet deep in trenches or ponds. Vertical loop systems use holes bored 150'-200' deep with U-shaped loops of piping. They work the same as horizontal loop systems, but can be installed in locations where space is limited due to size, landscaping or other factors.

Another type of geothermal heat pump is called a "Direct Exchange" or "DX" system. This type of system uses a much shorter loop of piping buried below ground, through which the refrigerant itself is circulated, replacing the heat transfer fluid used in other geothermal systems. Because the heat is transferred directly between the ground and the refrigerant, the amount of piping can be drastically reduced. This type of system is ideal for situations where the amount of space for the piping loop is very limited.

Gas furnaces and heat pumps have important differences in the comfort they deliver to homeowners. When the thermostat calls for heat, gas furnaces deliver warm air – approximately 125 degrees Fahrenheit. Air-source heat pumps delivers colder air – approximately 100 degrees Fahrenheit. This effect is more noticeable when the outdoor temperature approaches freezing.

The gas furnace has a life expectancy of approximately 20 years, whereas an electric furnace is 16 years and a heat pump only 15 years. In addition, annual maintenance costs for a heat pump will exceed that of a gas furnace.