Again, I said ideally. When will it ever outperform solar on a rooftop of the same size? How much more size could you get for the price?

It would never overcome its opportunity cost, even if it recovers it’s cost (which you’re speculating on and have no idea of the cost). You could spend the extra money for a solar car, or spend the money for rooftop solar. Rooftop solar will always outperform it for the price, so you have a negative opportunity cost.