I am not sure how to use this site, but I am a strong advocate of geothermal heat pumps, which maybe should have a category of its own.  There are numerous misconceptions about geothermal heat pumps.  The first is that they require alot of space.  This is true for horizontal loop fields.  For vertical loop fields, the boreholes need to be 10 to 15 feet apart.  I have a fairly standard house that required four bore holes, that is a square 10 feet on a side.  Not a huge area.  A second concern is the expense.  They are expensive, but for some reason, many contractors in this area size them too large, as was done with my house.  I have a four ton, 54000 btu/hr system.  If I were doing it again, I would not put in a system any large than three ton, and maybe two ton.  The following website from the Canadian government bears out my observations.http://oee.nrcan.gc.ca/publications/infosource/pub/home/Heating_and_Cooling_with_a_Heat_Pump_Section4.cfmI also buy all of my electricity from Xcel's WindSource program.  I like to claim I heat my house and put nothing into the atmosphere, though I know that is not entirely accurate.  I also calculate the operating expense of my system to be equivalent to using a 95% efficient natural gas furnace with gas at $4.60 per MMBtu. Since natural gas is over $10 per MMBtu, my heating bills are half that of a homeowner with a similar home and a 95% efficienct natural gas furnace.  Anyone with specific questions can contact me at vbstenswick@hotmail.com . VBStenswick