The US is pushing the use of plug-in hybrid vehicles, which use less gasoline than other cars, but are much more expensive. The cars replace gasoline power by relying on large batteries that can be recharged with an extension cord.

The federal government, hoping to soon regulate greenhouse gas emissions, is actively pushing for more plug-in development.

Barack Obama hopes to put one million plug-ins on American roads by 2015. His stimulus plan grabbed $2 billion for battery development, and several car companies plan to launch lines of plug-in hybrids.

However, the large batteries are expensive, and GM’s plug-in, the Volt, will sell for around $40,000, double the price of gasoline-electric hybrids.

“Plug-ins are not the perfect solution, they are not going to be the cheapest,” said Ewan Pritchard, manager of NC State’s Advanced Transportation Energy Center, who has converted conventional buses to plug-in hybrids.

Richard Lowenthal, founder and CEO of Coulomb Technologies, Inc, which sells charging stations, added that only one-fifth of the 250 million cars in America will have access to a garage area for charge.

The good news is, the United States should have plenty of electricity in reserve to power the plug-in cars.