Get an assessment done by MassSave directly, not an installer, they have one company contracted in different areas that all they do is the assessments and incentives, they are not installation contractors, so they aren't trying to sell you anything - they will match you with an installer after the assessment if you would like. (In my area that's ClearResult.) Several of the contractors also do assessments, but their focus is more on selling you the work they do than determining all the incentives you qualify for. I had one of the largest contractors do my assessment and they didn't care to answer my questions about MassSave programs that wasn't their main line of install work.