27% of North America's greenhouse gas comes from the production of electric power, so it makes sense to use as little of it as possible. That is why I am not as enthusiastic about ground source heat pumps as many others are; they run on electricity. If you are in a temperate part of the continent and can live without air conditioning, then there are perhaps better alternatives. One might be the NTS Matrix; Martin Holladay at Read the full story on TreeHugger