Besides emitting no pollutants or greenhouse gases, FCVs are about twice as efficient as gas engines. They also have a longer range than battery-powered electric cars and can be refueled quickly--in 3 to 5 minutes, compared with overnight charging for an electric car.

"Fuel-cell vehicles have no downside in terms of performance, and a lot of upside" in terms of efficiency and low pollution, says Daniel Sperling, head of the Institute of Transportation Studies at the University of California, Davis.

Since the early 1990s, automakers have built more than 500 FCVs for testing. Current models include the Chevrolet Sequel and Volt, the Honda FCX, and fuel-cell-powered versions of the Chevrolet Equinox, the Ford Edge and Focus, the Hyundai Santa Fe, the Mercedes-Benz A-Class, the Nissan X-Trail, and the Toyota Highlander (called the FCHV).

In addition to fleet testing, Honda has leased its first-generation FCX to two people in California for a subsidized $500 a month. "I've had fewer problems with it than any other car that I've purchased," says one of them, Jon Spallino, a chief financial officer at a design and build firm in Irvine, Calif. Spallino says he was selected partly because he had owned a Honda Civic GX that ran on natural gas. He has driven the FCX about 14,000 miles since 2005. "Right now there are only limited stations available, so I have to do some planning" for fill-ups, he says. His only minor complaint is that the car leaves a small puddle of water from the tailpipe on his garage floor.

The other driver is Q'Orianka Kilcher, a 17-year-old actress who played the role of Pocahontas in the movie "The New World." She got hooked on FCVs when she borrowed one for her movie's premiere, and earlier this year she persuaded Honda to let her lease the FCX. "It's really quiet," she says. "When I drive normal cars now, I can't stand the sound and the smell."

More FCVs, from General Motors and Honda, will be reaching consumers in the next year. (See Want to drive an FCV?.)