Payback time in Scotland is 6-ish years. Same seems to be true in Massachusetts. Solar Panels have a lifespan of around 25 years. Inverters may need to be replaced sooner than that, but still last at least a decade.

So it pays for itself 3-4 times over.

How often do you think solar panels need to be replaced?

>>By the time the "free" electricity has paid for the installation, you'll need to replace it.

You are going to have to back this up with credible citations. Otherwise it sounds like skepticism from 2008.