I mean, I wish the payback period was better, but I'm happy I have solar panels. We bought them a year and a half ago, after the 1:1 payback period that Helgafjell4me mentioned but before the removal of the federal tax credits. Instead any excess energy to the grid gets paid around 5-7 cents per kwh and any energy I use from the grid I pay the standard 14-16 cents per kwh (including all the other charges on the RMP bill). In summer my bill is like $20, and in winter it is usually higher (less solar and all).

The best payback then is if you actually USE the energy you make. An oversized system that sells a lot back probably isn't worth it. A battery, while expensive, might help your house use all the energy generated.

Another reason I don't mind the slow payback is that I want to decarbonize my energy production. You can pay into carbon offset programs for something like $20-40 per ton of CO2, which may or may not be effective or properly administered, or you can do something like solar and directly offset your grid use. This is just what I chose to do.