As I said in 2006:

Without too much exaggeration, you could say that today’s electric cars are really coal-powered. If you look at the sources of electricity in the US, “coal provides over half of the electricity flowing into American homes.” That means that in one ideal world of the alternative fuel crowd, when you plug your car in, you’re plugging it in to a coal plant (this is also why the idea of consumer carbon credits is catching on). The energy and environmental issues in the world are about far more than “gas guzzling” SUVs.

Now from USAToday, “Plug-in cars could actually increase air pollution.”

See also (from 2006): “Plug-In Hybrids Are Not So Green.”