Reply #9: Nowhere near enough energy density. [View All]

An electic car requires roughly 130 watt-hours to go one mile, taking the high-powered Tesla Roadster's example. Let's be generous and say 100 for an electric sedan. Now suppose that you put PV on the roof of the car--ten square feet of it. At a solid 15% efficiency, that's 150 watts at peak. That means that under ideal circumstances, assuming that it were parked in direct sun, a PV roof would generate enough power to drive a full 6-10 miles every day. That might be useful for a neighborhood runabout mini-vehicle, but when you're talking about full size cars with 150 to 200 mile ranges, it's not significant enough to bother with the cost of collecting that energy and converting it to a voltage suitable for charging. Particularly not when you're talking about a power savings of 10 cents a day or less.

Tesla Motors offers an option of a PV roof for your garage, which is larger and therefore generates a lot more power, but it's still trivial in comparison to what the car would typically demand for anything other than short commutes.