Its been a few years since I did the math, but last time I was quoted about 60K for a complete system - 60K at 5% dividend (NGG at the time), would give me $3K per year, enough to cover my bill.
AT the end of 20-30 years, a solar system will be worth nothing, or almost nothing, whereas I will still own the same stock in the same company hopefully the stock will have appreciated as well), and will still be covering my electric bill.
This of course makes lots of assumptions: I need to invest in company that will still be around for decades, that electric costs don't go thru the roof during that time, and the dividend doesn't go away etc. - but also would have to make assumptions about how long a solar system would last - its impossible for any of us to see out 30 years, but for the time being, I feel like on a purely financial basis, it didn't make sense for me today.
But trust me, I would love to pay one sunk cost today and not have to pay an electric bill for the next 30+ years, if only I could see that far in the future with some certainty.
We have some of the cheapest rates in the US, due to our nuclear, so our state incentives are fairly good to compensate. Nuclear may be discontinued, but given recent events I’m less sure. Either way I think we only have upside on the ROI due to rate changes.