This NY Times article looks into the current economics of going solar and comes up with a sour face. “Average payback is 14 years.”
Much is changing of course, from new technologies in the pipe-line, to rising fossil fuel costs, to proposed legislation, so that estimate will be different in a year, and different from one location to another. Commercial solar is another story and isn’t included here.
If you’ve been thinking about solar on the roof a couple of calculators are included.