To Diffusion founder Antoine Lecuirot, right, smiles as a salesman, left, shows an electric bike to a woman in front of the store in Paris. When the store first opened in 2003 few people here had heard of electric bikes, and turnover was mainly electric scooters. But in 2004, Lecuirot says the tide changed and now 80 percent of his revenue is from bikes, whose sales increased 70 percent.

New York ? When Honora Wolfe and her husband moved to the outskirts of Boulder, Colo., she wanted an environmentally friendly way to commute to her job as a bookshop owner in the city.

Wolfe, 60, found her solution about a month ago: an electric bicycle. It gets her to work quickly, is easy on her arthritis and is better for the environment than a car.

“I’m not out to win any races,” she said. “I want to get a little fresh air and exercise, and cut my carbon footprint, and spend less money on gas. And where I live, I can ride my bike seven months out of the year.”

The surging cost of gasoline and a desire for a greener commute are turning more people to electric bikes as an unconventional form of transportation. They function like a typical two-wheeler but with a battery-powered assist, and bike dealers, riders and experts say they are flying off the racks.

Official sales figures are hard to pin down, but the Gluskin-Townley Group, which does market research for the National Bicycle Dealers Association, estimates 10,000 electric bikes were sold in the U.S. in 2007, up from 6,000 in 2006.

Bert Cebular, who owns the electric bike and scooter dealership NYCeWheels in New York, said his sales are up about 50 percent so far this year over last. Amazon.com Inc. says sales of electric bikes surged more than 6,000 percent in July from a year earlier, in part because of its expanded offerings.

“The electric bikes are the next big thing,” said Frank Jamerson, a former General Motors Corp. executive turned electric vehicle guru.

They’re even more popular in Europe, where Sophie Nenner, who opened a Paris bike store in 2005, says motorists boxed in by traffic jams are looking for an alternative for short journeys that don’t involve navigating overcrowded transport systems.

Industry associations estimate 89,000 electric bikes were sold in the Netherlands last year, while 60,000 power-assisted bikes were sold in Germany.

The principle behind electric bikes is akin to that behind hybrid cars: Combine the conventional technology – in this case, old-fashioned pedaling – with a battery-powered motor.

The net result is a vehicle that rides a bit like a scooter, with some legwork required. Most models have a motorcycle-like throttle that gives a boost while going up hills or accelerating from a stop. On some models, the motor kicks in automatically and adjusts its torque based on how hard the rider pedals.

Although regulations vary by state, federal law classifies electric bikes as bicycles, and no license or registration is required as long as they don’t go faster than 20 mph and their power doesn’t exceed 750 watts.

Price largely determines weight, quality and battery type. A few hundred dollars gets you an IZIP mountain bike from Amazon with a heavy lead-acid battery. For $1,400, you can buy a 250-watt folding bike powered by a more-powerful, longer-lasting nickel-metal hydride battery like those in a camera or a Toyota Prius. At the high end, $2,525 buys an extra-light 350-watt model sporting a lightweight lithium-ion battery similar to a laptop’s.

Most models can go at least 20 miles before plugging in to recharge. Although the cost of electricity can vary, fully recharging the battery on a typical model costs less than a dime.

Joe Conforti, a commercial film director from New York, uses a 4-year-old model designed by former auto titan Lee Iacocca in the 1990s for running errands or getting to social occasions.

“It’s really nice,” said Conforti, who is eagerly looking to upgrade to a newer, more powerful ride. “If you’ve got a date, you go to meet friends – you go out on a (conventional) bike, you’re gonna sweat up. You go out in an electric bike, it’s great, it’s terrific, you’re not gonna sweat up and you ride home fine.”

Bike dealers said the growing demand goes beyond just the uptick in gas prices, but also because of word of mouth. Cebular said business at his store and on his Web site has been booming.