Geothermal heating / cooling systems are constructed by drilling a series of wells in the ground, roughly 100-150 feet deep. At this depth, the ground temperature remains at about 50-55° F year-round. The wells are connected in a loop to an electric pump that circulates a water/ glycol solution through pipes in the wells. The pump loop is also connected to a heat exchanger inside the building to be heated or cooled. During warmer months, the heat exchanger removes heat from inside, and transfers it to the water in the pump loop, where it is carried outside to the wells, and cooled by the earth. During cooler months, the heat exchanger operates in reverse, bringing in heat that the water picks up from the wells. A forced-air ventilation system then moves the heated or cooled air through the building. Geothermal systems only require electrical power necessary to run the pump, compressor for the heat exchanger, and the forced-air system fan, and tend to be more economical than other systems, such as natural gas, or oil. In addition, only one system is needed to both heat and cool, so there's less equipment to operate and maintain.