Plugging In for Less Pollution.

If more than half of U.S. motorists switched to plug-in hybrid vehicles, the country?s greenhouse gas emissions would plummet by the middle of this century, according to a July 19 study from the Electric Power Research Institute and the Natural Resources Defense Council. Several automakers are gearing up to their part, but major obstacles remain. Could the power grid handle such a widespread switch to vehicles that guzzle from electric sockets instead of gas pumps? Opinions differ.