Geothermal energy can be used to heat homes in the winter and cool them in the summer.
[The] 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 this by exchanging heat with the earth through a ground heat exchanger.
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.
They do cost considerably more to install, but can pay for themselves in 5-10 years and you then then have no heating and cooling energy expenses except for maintenance on the system.
Gepothermal energy holds a lot of potential. But its simplest applications need not be complicated or expensive: The Half Project notes that geothermal energy can be tapped as simply and cheaply as sealing up and insulating the crawl space under your house. Putting a basement under your home is also an application of geothermal energy.
Sorry: here’s the link. http://www.builditsolar.com/References/Half/ProjectsConservation.htm#Crawl