USA Today put together an interesting article on whether plug-in hybrids would be good for the environment. By putting the power supply onto the electric grid, you are taking the emissions problem away from the tailpipe and putting it into the coal plants that produce the electricity.
Plug-in cars could actually increase air pollution - USATODAY.com
By James R. Healey, USA TODAYSome proponents of plug-in hybrids feel that electric power plants can be regulated more easily.
The expected introduction of plug-in hybrid electric vehicles could cut U.S. gasoline use but could increase deadly air pollution in some areas, two reports say.
That's because a plug-in's lower tailpipe emissions may be offset by smokestack emissions from the utility generating plants supplying electricity to recharge the big batteries that allow plug-ins to run up to 40 miles without kicking on their gasoline engines. Plug-ins, called PHEVs, are partly powered, in effect, by the fuel used to generate the electricity.
About 49% of U.S. electricity is generated using coal, so in some regions a plug-in running on its batteries is nearly the equivalent of a coal-burning vehicle. The trade-off is one that even plug-in backers acknowledge. It could undercut the appeal of vehicles that appear capable of using no gasoline in town and hitting 50 to 100 mpg overall fuel economy.
If large numbers of plug-in hybrids were being recharged with power from the least-sophisticated coal plants, "There is a possibility for significant increases of soot and mercury," says a report by environmental advocacy group Natural Resources Defense Council. Soot particles can make it hard to breathe, especially for asthmatics. Mercury is toxic.