A couple years ago, we purchased and had installed a solar system. In MA, there is an incentive program called SRECs, which is a program where the utilities have to buy MWH of produced electricity, and I can sell my MWH of produced electricity -- that's tracked as an SREC. I can sell SRECs for 10 years, I make about 5-6 a year, and they go for 200-300$. It makes the payoff on the system about 4 years, and ROIC about 17%. If, when I go to sell, the 10 year window on the SRECs haven't finished the buyer and I will have to come to an arrangement for the remaining credits.

IMO, solar generally complicates all housing related transactions, but it's worth it.