The building is a 2 story workshop / garage, and has a man cave like area upstairs with tv, couches, and workout equipment. Solar powers it entirely and he gets credits back from the power company for putting power on the grid. I thought he was really happy with it, but said he woudln't do it again. Even in Washington state with generous credits, he doesn't think there will be a return on investment at all because by the time he earns enough credits to pay for it, panels and other equipment will need to be replaced.
I have put in serious thought into a Tesla roof on my place, but in the end might just get a couple panels and do a hobby build on a part of my roof to power our garage freezer and charge up my Model Y. Not that electricity here is expensive, I pay like 8-11 cents per KWH depending on if its peak or off hours, but I just like the idea.