This is the problem still in the US. Even at ~$0.23/kwh delivered in the northeast, you're looking at an ROI of nearly five years. Fine if you can float that kind of cash to feel better about yourself, but the economics just aren't there for most people, especially in cheaper parts of the country where rates are ~$0.12. Even financing you're looking at a monthly payment equal to or greater than an electric bill. Of course if you have the time to amortize it you'll come out ahead, but there's simply no cheap solution that can actually save real money out of pocket in any reasonable amount of time beyond theoretical future savings on paper. It will never be a true solution without massive subsidisation that reduces out of pocket to a 1-2 year horizon.
The way that these discussions get contorted online will never make sense to me. The same people who make comments about ROI and it not making financial sense also have new car-loans on vehicles that depreciate catastrophically and are worth nearly nothing in 10 years. After 10 years my solar install will have been paid off for three years, I will get free electricity, and I will have the following benefits along the way:
Additional home value/equity
Backup power in case of grid problems or catastrophe.
Free fuel for my used battery electric vehicle. (compared to ~$200 a month in gas)
As close to zero carbon footprint as you can have in our contemporary world
And that's all assuming electricity prices stay the same. That's not even talking about how hydrocarbons are a very finite resource. Saying there's no "ROI" is looking at the situation like the only variable is your monthly expenses. It's the best decision anyone with a home who has the climate can possibly make. If you value your independence and personal security you'd be crazy to not do it. What would you pay, if you have the kind of money most people on these forums do, to ensure your home operates independent of external inputs? Imagine a new great depression? Or other such event?
Three years ago, I was paying about $0.12/kWh, now it's about $0.22/kWh and installing a system makes sense.
It's cash up front for a savings later. My roof was due for replacement 'soon' but not immediately, and I didn't model the cost of moving that 3-5 years from the future to the present.
If you can't manage a 5 year planning horizon on a house, I'm not sure that home ownership is a great idea.
I get it if the ROI is 10+ years... too much uncertainty to put a lot of capital in.
That's 15% yearly