In response to the last post's comment, here's a bit of my thinking on the solar panels. I've been checking into a radiant heating supply company that uses the potable hot water lines to supply radiant heat through a closed system. Some of the benefits are moderate cooling in summer, reduced fuel costs and a simple, easily installed and maintained system. The basic idea is to heat water through the hot water tank and then send it through a system of radiant heat lines under the floor. But with our unobstructed, south facing roof we could add solar panels and "preheat" the water before reaching the hot water tank and store the heat in the basement slab. This would further reduce the fuel required to heat the water for showers, dishes and warming the house.
The only trouble is the systems are so interconnected that a firm commitment is required. The basement slab would need to be poured with tubing in place. The plumbing needs to be run before walls and joists are covered up, then there's my dream of replacing the shingle roof with copper and the need for a new hot water heater. All this just to provide an additional heat source - which is not a new concept for our house.
We have two old coal bins from before the furnace was converted to gas, and have found a letter written by the PO to the furnace manufacturer. He apparently wanted to know if different types of coal could be used and the answer was yes. So they were stockpiling cheap coal. We have also found disconnected gas lines that run to all the ceiling electrical fixtures. Because of the electrical wiring setup I don't believe the gas was ever used, but was still available if that new fangled thing called electricity went belly up. So I feel confident about mixing solar generated radiant heat with our gravity feed, gas furnace and wood burning fireplace. But we'll probably just put on an extra sweater anyways.