But you might get that kind of condition 10% of the time. Also solar panels are even more inefficient than I thought. You can only expect 30% of incident light to become electricity.
As far as i know the amount of power per square meter is about 1kw, then you have the efficiency of the solar panel (a nice solar panel has about 20% efficiency), then you have the orientation of the surfaces of the car and the total area of the car and then you have the efficiency of the DC-DC regulation circuit. A solar power system embedded into the surfaces of the car would be useful only for partially powering the air conditioning system and trickle charging the battery (an example of this is the Nissan Leaf). No, it would not be a very good idea. If you want to see solar cars working google solar car and look at those streamlined things that look like UFOs.
IIRC the solar-only car couldn't manage much above walking pace... My view of Tesla cars is bit like that my view of the Occulus Rift... It may be good, it may be 'the future'... but 'the future' is still what it is - it's the Wright bro's plane... An example of what's possible but we're still a few years away from a 747...
50+ mph solar cars have been around for a while; we're hopefully going to be entering ours into the WSC next year. Basically, the potential boost in range of PV cells isn't negligible (probably 10% in good conditions) but they are expensive.
