Just have a first free estimate coming back, saying that my roof can possibly generate $5000 - $5800 per year, which is a system around 6kw. Payback period should be around 7 - 8 years. ROI of 11.5%
I have a friend in California in the solar panel business; he wired up his roof and makes a profit each year off sales to the local utility. He showed me how during the day his power meter actually runs backwards while he is generating more power than using; at night it reverses and he draws power off the grid. It seems like common sense to promote solar/renewable energy.