Given the durability of panels, it'd be fascinating to see roof redesigns, and some changes in panel packaging, that standard large rectangles become the basic components of a 30 year roof. Or as siding. I've seen them used vertically on the Southern walls of commercial buildings in Alaska, and they looked great.
Absolutely. Energy has to be baked into every structural element. Either producing energy, or storing energy, or providing insulation, or acting as a transfer medium (heat pump).
Why don't they do this for cars?
I'd imagine the difference between flat and curved, in addition to very different wear patterns, and inability to get your desired color.
Even slight changes in packaging to adapt the panels to a structural material might increase cost. But doing custom shapes to fit the panels of a car? Getting just the right shape? That's an entirely different manufacturing process nothing like what currently gets produced.
The benefit on cars is also pretty small, at least whenever I've bothered to calculate it. Cars need a massive amount of energy compared to a house, and have far less surface area.
…which is also never in an ideal angle for production..
Sono Motors tried it and went under..
In theory, it sounds great and even obvious, but once you get into the details - not so much..