Technically it doesn't give you 25% per year, but I'd argue what it does is - for this purpose - better. You get free electricity which is estimated to be worth 25% per year.

If the Buffoon manages to blow up fossil fuel prices to the same degree Putin did, your payback time might shrink to 12 months instead.

It doesn't give you 25% a year, because you don't have your investment anymore (or most of it, if there is a second-hand market.) After the first year you'd have a -75% return, after the 5th you'd be at an effective annual 4.5%, after the 10th at an effective 9.5%.

It goes up from there, but it takes a while to become an investment better than alternatives. Inverters start failing after 10 years, too, and they're half the cost of a $400 setup, I believe.