> The only problem with this of course is that the range of a car is already limited. Plugging in your car overnight, and then discovering half the charge is gone might be a tad, shall we say, unwelcome.

Indeed.

However, electric cars could have a part to play in equalising electricity production & demand. Electric cars could be re-powered by removing the battery pack and inserting a new one (this would be done at the successor to petrol stations; obviously battery packs would all be the same size and have the same interface). The battery station would then need to recharge all its spare packs -- and it could do it at the times when electricity supply exceeds demand.