However, the majority of electricity in the is generated using power stations fired by coal and gas, and hence even if a substantial substitution of the present oil-fuelled cars by electric vehicles could be made, it would entail the consumption of vast quantities of these other fossil fuels instead to provide the additional electricity for them.
It is claimed in a Royal Academy of Engineering (RAE) report on electric cars that they are in any case cleaner because 80 - 90% of the energy put into them in terms of electricity is recovered in terms of useful power at the wheels, to be compared with 20 - 30% in a conventional oil-powered car. Well, that sounds good, but the reality is that only about one third of the energy in the coal or gas actually ends-up as electricity because of the Second Law of Thermodynamics and the Carnot Cycle limit - the other two thirds being thrown away as heat. Thus the electric car is harvesting in terms of well-to-wheel miles only about 27% of the original fossil fuel energy, so not that much better than the standard car running on petrol or diesel... by 2020, 1.7 million electric cars should be on Britain's roads, or just over 5%, which I don't honestly see would make a serious hole in our demand for imported crude oil.