[citation][nom]magicandy[/nom]They weren't saying that coal is the largest source of energy in the US, they were saying that it accounts for the largest amount of greenhouse gases, which is true even though it's not our most widely used form of energy production.[/citation]
The point is that running a car on electricity made from coal produces less greenhouse gases than running a car on gasoline.
Right now, U.S. electricity is roughly 50% coal, 20% Natural Gas, 20% Nuclear, and 10% Renewable. With that mix, electric cars produce 40% less greenhouse gases than a regular gas engine car, and that includes the emissions for building the car. As the mix changes more towards renewables, electric car emissions become even better.
And by the way, using coal to power cars near term not only lowers greenhouse gases, it also keeps the money from going to terrorists.