I’ve written about this in many other posts, I’m all for it, but in this thread I am focusing on what’s more practical.

I’m afraid you’ve fallen victim to bad math if you think that paying for your system up front is much different from financing it over time. For any expensive purchase, those two approaches are considered equivalent. For example, most people have a mortgage. So $20K spent on a solar system is $20K not put in to paying down the mortage, which results in exactly the same numbers. If you are debt-free, the $20K can be put in the stock market and it will pay back quite a bit more per year than the cost of buying grid power to match the output of the PV system — and you’ll still have the principal too.

This is one of the classic examples of the bad math, and it’s remarkably common so don’t feel too bad about it. Value received in the future for money paid today must be discounted, there is no way around it, no matter how you pay for it.