Well first, if it takes you 20-30 years to break even, you’re getting ripped off, or your loan’s interest rate is terrible and you’re making minimum payments. Solar panels have warranties that basically match the life of a roof these days, so ideally, you’ll replace that roof at the same time as putting up new panels. Solar panel tech has come a long way in 25 years, the optimist in me says 25 years from now they’ll be cheaper, more efficient, and more reliable than they are today.

In theory the electric rate will go up and your monthly solar panel cost will stay the same. But yes you should not get solar unless you are getting a new roof or recently got a new roof. Most people break even much sooner than 20 years - often 7-12 is what I hear.