I'm not trying to second guess your decisions.

My experiences are at least a decade old. Payback on various options depends on the relative cost of energy in the location being studied. Cost of fuel oil, electricity and so forth varies greatly from area to area.

In our area resistence heat of course was the most expensive per million btu, with oil next and lp gas next. Natural gas was king because of local supplies being plentiful.

The nice thing about geothermal is it helps a lot on the cooling side, so if you are in a place where cooling is used more months it will pay back a lot sooner.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.