I've found that spreadsheet to be pretty accurate, and I'd agree that switching to propane wouldn't save you anything. Current NY state propane prices here: http://www.nyserda.org/energy_information/nyepf.asp We recently were looking at the same thing, as a recent back injury took me out of my usual firewood harvesting. The last time I had to fill my oil tank I paid $1.50 /gal and was in for a shock if I went back to oil. Couldn't see throwing money at an oil budget plan, so we decided to go the geothermal route. Ground loop just wemt in today. Lots of money up front, but with the 30% federal incentive, payback over oil should be around 7 years for us.