You're not far off on the math for the most efficient cars, but I can't even get that much solar on top of a 23' camper, and that's with full sun and assuming I can park directionally. You're talking about 80 sq ft. Even taking into account these more efficient panels, you're looking at maybe 10 mi a day range added, best case.

And that's assuming you're parking outside at all while at work. In suburbia you might be. Good luck in any big city.

Overall I don't see how this is going to be economically efficient any time soon, even in the best use cases. It seems better to have fixed solar and a plug. But I hope I'm wrong.