What happens if you use the free energy from the solar panels on your house? That seems to me to be more efficient than oil-powered cars and certainly cheaper (assuming you don't but a ridiculously expensive electric car that will take you a lifetime to recoup the costs of).
It would not be more efficient since it will take a longer time to charge electric cars using the free energy from the solar panels unless someone can invent a more convenient solar panel that can speed up the electric car charging to at least an hour. Nevertheless, oil-powered cars would still be better to use in long-distance travels since refilling up their tanks is faster than waiting for an electric car's full charge.