Major auto companies worldwide see electric cars in their future, and a lot of motorists are driving them today, mostly in the form of gas-electric hybrids.

The industry's U.S. trade group met in Washington recently to focus on some of the technical and policy challenges they face. And those challenges are numerous.

Gasoline- and diesel-powered vehicles today store their fuel in a metal tank. Electric cars store theirs in a battery. Battery technology has been improving rapidly, but Nancy Giola of Ford says it's still a major roadblock.

"The biggest challenge, and we've heard this repeatedly, remains the battery. Questions remain about the durability in real world use, safety, and of course affordability in the cost equation," she said.

General Motors has been touting the Chevy Volt, a plug-in electric car that is due out in 2010. GM official Tony Posawatz said if they sell around 200,000 a year, they will be the world's largest buyer of lithium-ion batteries.

"When someone asks me, 'Where do I get these cells from?', today the only choice I have is to go overseas and look at Asia."

Posawatz says importing the batteries adds several hundred dollars to the price of each car. It's also a security issue: some American analysts worry about cars dependent on foreign batteries almost as much as they worry about cars dependent on foreign oil.

The U.S. electric power industry is excited about the prospect of fueling the next generation of cars and trucks. Thomas Kuhn of the industry's trade group, the Edison Electric Institute, says people will be able to refuel right at home.

"We can wire up in houses easily where there are garages, and where there are not garages, we can rev up in parking lots," he said. "So there is going to be an electric infrastructure need, and we think we can move that [forward] very, very quickly because electricity, fortunately, is everywhere."

Critics note, however, that many urban dwellers, for example, park on the street, not in a garage.

Environmentalists worry that the increased demand for electricity will just mean more coal burned in power plants. Coal supplies half of U.S. electricity now, and renewable resources like wind and solar are strongest in areas that don't have a robust grid to get the power to consumers.

Democratic Senator Byron Dorgan of North Dakota said the country needs what he calls a "transmission superhighway."

"And we need it because you can't produce wind from Texas to North Dakota and solar across the Southwest and other forms of energy where it exists in the renewable form of energy unless you have some place to put it on a wire and move it where it's needed. So if we're going to produce more, and we certainly have the capability, we need the transmission ability to move it."

The internal combustion engine has dominated the motor vehicle business for a century, but it wasn't always like this. At the beginning of the automobile era, gasoline-powered cars competed with electricity and steam, and Ed Cohen of Honda says the future may look like that, too.

"Every one of these technologies - hydrogen, natural gas, battery electric, gasoline; you can improve the internal combustion engine and make tremendous strides in that regard," Cohen said. "They're all going to be a part of this mix. And each technology is going to appeal to a different type of consumer."  

Despite the challenges of moving from petroleum- to electric-powered transportation, the head of the industry group Electric Drive Transportation Association, Brian Wynne, sees a bright future for electric vehicles.

"There's a growing recognition that electrification of transportation is critical to reducing our oil consumption, reducing our greenhouse gas emissions, spending more of our energy dollars domestically, and building green jobs for the future."

Each year, American consumers have more choices. Honda introduces its new hybrid Insight car next year, and the first plug-in hybrid debuts the year after that. On the other hand, conventional gasoline and diesel vehicles are expected to dominate U.S. highways for many years to come.