Yah I did a full breakdown and worked out all the numbers* to calculate the time period till payback (4-6 years) after which there will be some end large profit from the tail end of the MA SREC's and then small but continuous "profit" from very little to no electric bill (depending on my AC usage). After all the work I did my numbers were very close to the quotes I got.

After the immediate state rebase + fed and state tax rebate I am only paying ~3cents/Watt

Any particular number you want to know? Say the system costs 24K, MA does a straight rebate to the installer so you would only have to write a check for say 18K, and come next tax year get 6K from the fed and 1K from MA back so the 24K system would cost you ~12K. The SRECS pay that back between 3-7 years and that is guaranteed $300/MW till 2020 so by doing the install this summer I should pay it off around 2018 and have extra income until 2020. Oh and it doesn't count against property tax for 20 or 40 years (forget which).

The main reason I am doing the switch is that it is a small investment that is _extremely_ stable with 1) a 100% return with interest in ~6 years on the electricity 2) increasing the value of the house by ~20K (more than post tax check!) and 3) will continue to generate electricity/tax free income for as long as I live in the house potentially the equivalent to the initial cost several times over. Not a bad small investment.

* Electric usage est, electric cost growth est (power costs more every year in MA), sun hours (obtained from various government sites) est, SREC payback est, power est, angle of house and roof.