Well that’s a whole other question. In Australia the payback period is usually very short (a few years or so), and therefore financially a no brainer. I know systems are consistently a lot more expensive there for some reason.
I’ll need some details to see if that 25yr payback is ballpark. What is the quoted price for the ~5kW system? How much do you expect to get back from tax credits? How much do you pay per kWh for your electricity (let’s say peak pricing).
Marty