Don't forget to improve the thermal efficiency of your property otherwise no matter what method of energy generation you use, it all goes out the window, floors. roof etc. Just by putting an insulation material between my floor joists I saving about 6000 therms of gas a year, I've taken a room at a time, usually when redecorating the room, by just lifting the sections of floorboards and laying down an efficient insulation material leaving a circulation gap has reduced our gas heating consumption quite dramatically to maintain the same room temperature. Not very expensive and almost immediate payback, for just a few hours work per room.
