My 8K Solar system was $30k. I bought outright. Had $9,800 in rebates and saving $2-$3K per year on electric. Estimated pay back is ~6-7 years. If I had invested the $30K in high yield savings (2.2%) and used it to pay my bill at $200/month I would have $16,845 at year 7. Conservatively invested earning 4% I'd have $20,325 and Market rate index funds (7%) I'd have $27,300.

If I add in the additional cost of insuring the panels, expected maintenance costs, etc. The real payback is likely 8-10 years.

That was buying outright. Taking out a loan or leasing panels is a much worse return. Don't invest in solar panels if you're looking to save money. There are many better ways to do that. Invest in solar panels if you want to reduce your energy footprint.