I looked into this extensively about 3 years ago, but in the northeast with a well insulated house. I ended up going with air-source heat pumps rather than geo

I looked into this extensively about 3 years ago, but in the northeast with a well insulated house. I ended up going with air-source heat pumps rather than geothermal. The geothermal units were less expensive, but the drilling was massively expensive. Air source heat pumps now work down into pretty cold temperatures. With a high-efficiency air source our average heating/cooling bills are around $250 (down from ~$400 with older models). Even if ground-source got that down to $200, the payback period of the drilling would exceed our expected time in the house. We still kind of wanted to do it, but the added problem was that no one in the area was really experienced with ground-source installs. So we would be dealing with the hassle of trying to get these HVAC guys to work on projects that they are not that interested in. In the end we went with air-source, and it worked out very nicely.