The batteries are often rated for 20 years, after which you're down to 80% capacity, they don't simply stop working. Solar panels are rated for 30 years. So yeah, pretty hands off.

As for why do it, well, a right sized system allows you to be independent from the utility company so if monthly financing for it falls to the same ball park you're paying for electricity already you've simply locked in a rate and hedged against further price hikes.

If I was paying on average $99/mo to PG&E or whomever I'd eyeball a $12,000 system financed over 10 years. That would get you about 20kWh storage and enough panels to keep it full which may or may not be enough for your house.

That crossover point obviously varies from house to house and what's available to you locally. I think it makes a lot of sense for new houses, that way they might avoid a potentially very costly hookup to the grid which in some locations is tens of thousands of dollars in itself.

I’ve never understood the calculations people make to justify that solar roof panels save them money.

Every time I do the calculations, it’s money loss.

If you want to install them for environmental reasons, great. But don’t kid yourself that’s is a great investment. It’s not. Putting the money into an S&P 500 index fund for 14 years is a better investment. It will double about twice in that time.

If everyone does that, all your stock won’t be worse much when the world will be either at war or starving. People have kinda forgot to think long term clearly. Also, you must live in a country where the politics are very anti climate. In my country it’s a good investment to install solar power.