If my memory serves me right: a few years or so ago I had a client that received geothermal heat pump credit. The cost to buy it and INSTALL it, in total, was very EXPENSIVE. I think this is mainly used in RURAL areas, where they do not have natural gas lines, and use oil or propane gas to heat their homes. This geothermal heat pump that my client bought and had to pay someone to install was very expensive because they had to drill down into the ground. I double checked everything to make sure everything was legitimate, and they were entitled to it, which was a large credit. At that time , I do not think an average person could afford this. Just for what it's worth.