Should be able to produce more than vampire drain - let's say you manage to squeeze a .5kW array onto the car - could generate 2.5 to 3 kW max on a sunny day in the right part of the world. Perhaps not enough to justify the inclusion, although I personally feel this kind of configuration will become commonplace on certain types of vehicles as we see PV tech improve, especially with regards to Perovskite and thin film panels. Broadly speaking a LWB panel van (VW Transporter, Renault Traffic etc) should afford 7 - 8 m2 space using the roof and bonnet, allowing for a maybe 1kW system, thus perhaps 5 to 6kW could be achieved with the same caveats.
There are some issues associated with this. Obviously seasonal and locational sensitivity - this kind of thing would be great here in Brisbane during summer but not so great elsewhere. There are some technical factors too - the panels will provide a relatively low voltage which will have to be stepped up drastically to charge the high voltage pack. Not to mention you have to park your car in the sun all day - not ideal for most :tongue:
A better idea for all intents and purposes is to put the same array on the roof of your house - let it power your house, charge the car and collect more sunlight (depends on the roof positioning). Plus you get to park your baby under cover too. Note: this option may require a house. House sold separately.