At a minimum, you want to know what kind of system is in place, how old it is, what condition it’s in, and how much it’ll cost to operate. Typically, you’re not going to select or reject a house because of the type of heating system it has or doesn’t have, or because of the size of its hot-water heater. On the other hand, if you’re buying this house on a shoestring and would have to declare bankruptcy if you had to replace so much as a fuse within the first six months, then the house with the newer heating system will obviously be more appealing than the house with the furnace that will have to be replaced before next winter. Generalizations about comparative energy costs and the relative merits of different systems and energy sources are problematic, since so much depends on the climate and the cost of energy where you happen to live. The type of dwelling, the age and kind of the system, and your life-style also have a lot to do with how high or low your energy costs will be. But with those limitations in mind, you can use the following considerations as a guide in weighing the pros and cons of the various systems you may see.