I don't know what numbers you're running, what you guys are stating makes no sense to me.
Do anyone of you even touched a solar panel IRL? Seen one? Bought one?
I'm not sure how touching one would enlighten me about the numbers behind buying one but whatever.
In central EU it would cost me about $7200 to have a decent (5kw) unit that would provide me with 630 watts 0-24h on average.
Using 630 watts 0-24h with $0.14/kWh costs $760 a year so that's over 9 years before reaching ROI.
So yeah, you might be able to get your hands on some super cheap solar panels+inverter+batteries but I'd much rather pay the $0.14 with a grin on my face and spend that $7k on more hardware.
Yeah, depending on where you live, there are some pretty serious subsidies as far as renewables go.
But that's a completely different topic. You're essentially buying a solar panel to deal with the power grid, not mining. It wont make power any cheaper for you as selling it back to the grid earns you money too (sometimes more then the cost of the power normally). I guess it really depends on how much power costs are for you normally. If you're over 50% of your mining revenue in power, it'll probably be better for you. But if you're at something like 30%, it's not going to matter.
ROI takes a really long time. However, you'll probably never need to get rid of solar because the price of BTC crashes, so it's a much, much, much safer investment. I don't think people really understand how risky crypto mining is. Mining with AMD hardware was literally destroyed for the average joe by a couple developers that got greedy. Like an entire generation of miners were wiped off the map due to a couple private kernels. I really don't think a lot of people understand that... Literally the ASICs of the GPU market. That could still also happen with Nvidia (which is why I push a miner fee so hard).