I was pleasantly surprised upon reading this article about converting hybrid cars to electric plug-ins that CNN is finally starting to acknowledge that electric cars are not the be-all end-all solution some people think they are.
The problem is that the electricity has to come from somewhere, and right now around 70% of the electricity in the US comes from fossil fuels (50% from coal burning, even). It's *better* than using gasoline though for a few reasons - such as that remaining 30% that comes from water, wind, solar, and nuclear (which technically is also non-renewable, but does not have the greenhouse gas problems of fossil fuels instead adding disposal problems). In addition there is economy of scale in power plants - rather than having a small engine and generator inside the car, power plants have a number of large ones. These tend to be much more efficient in terms of both higher power output compared to fuel input, and also lower pollution output compared to fuel input. Because of both of these higher efficiencies, the energy from plants tends to cost less than the energy from gasoline.
So in the end, yes it's good to change your car to electric only, but you will still be paying a higher electricity bill in the place of a gasoline bill, and it's NOT a perfect solution as of yet. Fuel cell cars also aren't a perfect solution, but with more research we'll continue to improve our options.