An air-source heat pump can deliver one-and-a-half to three times more heat energy to a home than the electrical energy it consumes. Unlike furnaces that burn natural gas or heating oil, heat pumps are powered by electricity and move heat rather than converting it from fuel. Because there’s no combustion or air pollution produced at your home, heat pumps save energy, greenhouse gas emissions, and air pollution. Heat pumps have some impact on the environment as they need electricity to run, but the heat they extract from the ground, air, or water is constantly being renewed naturally. They are also extremely efficient, low maintenance, and have low operating costs.
Air-Source Heat Pumps
A heat pump draws heat from the air or earth and uses that energy to heat or cool a house. The traditional air-source heat pump extracts heat from the outside air during the heating season and releases it to the outside air during the cooling season. Heating and cooling is accomplished by moving a refrigerant through the heat pump’s indoor and outdoor coils. Like in a refrigerator, a compressor, condenser, expansion valve and evaporator are used to change states of the refrigerant between a cold liquid and a hot gas. Similarly, heat pumps can also operate in a cooling mode where the cold refrigerant is moved through the indoor coils to cool the room air.
Ground-Source/Geothermal Heat Pumps
Ground-source heat pumps are similar to ordinary heat pumps, but use the ground instead of outside air to provide heating, air conditioning and, in most cases, hot water. Beneath the surface, the ground stays at a constant temperature, so a ground source heat pump can be used year-round.
A ground source heat pump circulates a mixture of water and antifreeze around a loop of pipe – called a ground loop – which is buried underground. Heat from the ground is absorbed into this fluid and is pumped through a heat exchanger in the heat pump. Low grade heat is then extracted by the refrigeration system and, after passing through the heat pump compressor, is concentrated into a higher temperature useful heat capable of heating water for the heating and hot water circuits of the house. Ground loop fluid, now cooler, passes back into the ground where it absorbs further energy from the ground in a continuous process while heating is required. The length of the ground loop depends on the size of your home and the amount of heat you need – longer loops can draw more heat from the ground.
The Department of Energy requires all air-conditioning and heating equipment manufacturers to evaluate and rate the efficiency of their equipment on a seasonal basis. These ratings are known as the SEER (Seasonal Energy Efficiency Rating) and the HSPF (Heating Seasonal Performance Factor). The higher the SEER or HSPF rating, the more efficient the heat pump. High-efficiency units cost more, but since operating costs are lower, the payback period may be shorter than you realize. A high SEER/HSPF heat pump also can add value to your home which is important to today’s energy-conscious home buyers.
Federal Tax Credit
Homeowners who install ENERGY STAR qualified geothermal heat pumps may be eligible for a 30% federal tax credit.