The minute you have a plug-in hybrid, you can put solar cells on the roof, or an extendable wind-turbine and hey-presto, an almost fossil fuel independent vehicle!
This is NOT science fiction, the numbers really do pan out for significant benefits (ie > 6,000 miles p.a. from the solar, >20,000 miles p.a. from the wind turbine).
(like this guy, who gets most of his commuting range from wind and solar)