"A geothermal heat pump system is a heating and/or an air conditioning system that uses the Earth's ability to store heat in the ground and water thermal masses. These systems operate on a stability of underground temperatures; the ground a few feet below surface has a very stable temperature throughout the year, typically somewhere in range of 50-85 °F (10-30 °C) depending upon location's annual climate. A water-source heat pump uses that available heat in the winter and puts heat back into the ground in the summer. A geothermal system differs from a conventional furnace or boiler by its ability to transfer heat versus the standard method of producing the heat. As energy costs continue to rise and pollution concerns continue to be a hot topic, geothermal systems may hold a solution to both of these concerns. A particular advantage is that they can use electricity produced from renewable sources, like solar and wind power, to heat spaces and water much more efficiently than an electric heater. This allows buildings to be heated with renewable energy without transporting and burning biomass on site, producing biogas for use in gas furnaces or relying solely upon solar heating."
from wikipedia

According to the EPA, geothermal pumps "are the most energy efficient, environmentally clean, and cost-effective space conditioning systems available." ("Space Conditioning: The Next Frontier," EPA 430-R-93-004, April 1993) Call aur Solar at 414-463-4287, and we can set up a site evaluation, or help you to set up a geothermal system at your home.