Geothermal
Geothermal heat pumps (GHPs), take advantage of the constant temperature of the shallow earth (40°-70°F/4.5°-21°C) to efficiently exchange temperatures, heating homes in the winter and cooling homes in the summer.
Although many parts of the country experience seasonal temperature extremes—from scorching heat in the summer to sub-zero cold in the winter—a few feet below the earth's surface, the ground remains at a relatively constant temperature year-round.
This ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. The GHP takes advantage of the constant subsurface temperatures by exchanging heat with the earth through a ground heat exchanger.
The ground provides a type of thermal energy storage, which allows GHPs to act as a heat sink—absorbing excess heat during summer, when surface temperatures are relatively higher—and as a heat source during the winter, when surface temperatures are lower. This increases efficiency and reduces the energy used to heat and cool homes.
As with any heat pump, geothermal and water-source heat pumps are able to heat, cool, and, if so equipped, supply the house with hot water. Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings. Relative to air-source heat pumps, they are quieter, more efficient, last longer, need little maintenance, and do not rely on the temperature of the outside air, which is more variable than the ground temperature in most climates.
A dual-source heat pump combines an air-source heat pump with a geothermal heat pump (versus a dual-fuel heat pump, which combines natural gas heating in combination with an air-source heat pump). These appliances combine the best of both systems and can switch between air-source and ground-source depending on what mode is better for the load required.
