I can’t really tell you about your situation, but my wife and I did the math for our ROI on a set of roof mounted panels by assuming that the power company would continue raising rates. We averaged the delivery increases and generation cost increases over the number of years we had been in our home, then ran that annual increase over the lifespan of the panels. Rather than being a twelve year break even point it worked out to about seven. In our case, Maine has okay laws about net metering so check what your state and municipality’s regulations about it are. Look at your overall financial picture. If you can’t do it without a loan, shop for your own loan rather than just taking the installer’s.

To answer your question anecdotally, this past summer we were very happy to only pay our grid connection fee of $18 monthly while our neighbors complained about $300 (or higher) each month. You might not hit your full generation needs, but you might make enough of a dent to make it worth your investment