I'm looking into it for the renovation of my house. The incentives are basically these:
- The State will pay for half of the equipment cost.
- the feds and state give you a tax break, but the feds have a tax on the tax break!

So I was looking at a 4.2 kW system for my house. I think it's like 20 panels on my roof which optimally will product 5000 kWhours of electricity per year.
The cost of the equipment and intall is in the neighborhood of $36,000. The state pays $16,000 of that, so I'd have to shell out about $20,000. Then on my taxes, I'd realize around another $7000 in savings. So ideally, the set up cost me about $13,000, and then I can theoretically save about $500 - $700 a year in electricity costs. That works out to about a 5% return, assuming my electricity costs don't go anywhere over the next 20 years.
Not stunning by any means, but the environmental effect seems quite good.
Comments??