“I did the math and even with zero percent interest, he was paying almost double for the solar panels than he was paying for his electric bill.”
Yeah, but think about the warm feeling they got!
The only way it might pay in the end is if you do it yourself.
I built the 14kw battery banks for about $3000 each. If you buy that as a packaged box its more like $10k.
If you or a family member doesn’t have the know how, you will overpay and never recoup.