I will chime in since I just installed a 7.65 kW system mostly to offset my electric bill from mining, however, it is completely a grid-tie system. I paid $.65/watt including shipping (bought from a wholesaler on eBay), $2800 for 2 inverters, installation was $1.10/watt (1 inverter would have worked if I went with SolarEdge w/optimizers). I had to take a break from mining when my Edison bill hit $900 last November for running about 8 TH. Not entirely sure if this system will help in ROI for running S7s, on the other hand, Edison buys back extra power @ $0.9/kW $0.09/kW..
so you spent around $15,000 for 7.65kW and no battery packs?
IIUC, that means you should get ~7kw*12h = 84kwh/day (~$8), and it will take roughly 2000 days, or 6-7yrs, to pay back the system cost assuming no surprises
as i understand, thats not too bad since solar insallations are typically advertised as around 10yrs to break even, at which point you might need to install $4000 of new panels to keep running another 10+yrs
That's why I never have been able to justify it. It's a long term investment. If you look at mortgage 6-7 years on a house to ROI is not horrible compared to many loan duration for a house.
But as far as bitcoin 10 year ROI point just does not fit well. So kinda 2 different investments. If it's all still working down the road in 10 years he will be very happy getting free electricity from the sun.