“Can you provide a source on the amount and nature of the subsidies to different sources of energy generation? “
This is the leading source about tax and other incentives.
http://www.dsireusa.org/
Be aware that while geothermal is extremely efficient, it usually has a very high initial cost, and it is a moving parts system, whereas most PV has no moving parts. If you are just looking at it to provide space conditioning, you may want to get some information on how your particular building may be able to be improved through passive solar, insulation, envelope tightening etc.
Thanks. I will check it out.
My issue is a little different. We have a 1750 house. We cannot tighten the house without losing important architectural features such as Indian Shutters. Solar is not an option because of the “look” of the house. I am planning on oversizing the unit for the square footage to compensate for the lack of wall insulation.