Next step is a geothermal ground source heat pump, and he hopes to someday charge a plug - in hybrid car from his solar panels. (treehugger.com)
The building is heated using ground source heat pumps. (treehugger.com)
To be able to use ground source heat pumps you need to have a garden, and one big enough to ensure that a network of pipes can be buried into the ground. (greenplanet.com)