Filed at 12:28 p.m. ET

NEW YORK (AP) -- 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 doesn'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 four-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.

''Fifty percent of that increase is probably because of gas prices, and the rest is that there's just more bikes out there,'' said Cebular, who has run his shop on Manhattan's Upper East Side for seven years.

Improved technology also has made electric bikes more popular, Cebular said.

''When I started, there was only one bike that had a nickel-metal hydride battery -- everything else was lead-acid and was 80 or 90 pounds,'' he said. ''That's a huge improvement.''

Jay Townley, a partner at Gluskin-Townley, said the latest electric bikes are sleeker, better looking and hide their often-clunky batteries better than ever. That goes a long way to attract baby boomers and other mainstream customers.

''The new designs that we've seen in the marketplace are going to inure to the benefit of the electric bike companies,'' he said.

Ultra Motor, an England-based electric bike and scooter company, is betting big that it can capitalize on what it seems as a growing market for attractive-looking two-wheelers designed specifically for U.S. commuters. The company on Tuesday unveiled its ''A2B'' model, a slick, low-riding electric bike.

Ultra Motor took a conventional bicycle and redesigned it with fatter wheels, a lower center of gravity and a thick shaft designed to hide the lithium-ion battery inside, U.S. Chief Executive Chris Deyo said. The result is a cross between a motorcycle and a mountain bike.

The company already has signed up 75 dealers nationwide to sell the $2,500 bike starting next month.

''A year ago, when you mentioned the word electric bike, people looked at you and they really weren't sure what it was,'' Deyo said. ''Today, what we're finding is we're actually having dealers call us seeking an electric bike to meet the demand.''

Jamerson, the former GM executive who has become a staunch advocate for electric transportation, believes this is only the beginning for electric bikes. He retired from GM in 1993 after helping develop the company's EV1 electric car, and he's been an avid follower of alternative transportation ever since.

The EV1 project, though widely seen as a spectacular failure, helped convince Jamerson of the value of electric transportation. Given soaring fuel prices and thinning patience with foreign dependence on oil, Americans are ready to embrace electric vehicles, he said.

''Did you know there are 70 million electric bikes on the road today in China, and they are selling at the rate of 2.6 million electric bikes a year?'' he said. ''The public at large needs to understand that it is the right thing to do to move to electric transportation, and electric bikes and electric scooters will allow you to do that, to get that familiarity.''

As for Wolfe, she could not be happier with her bike, a 48-pound mountain bike with a lithium-ion-powered assist made by California-based IZIP. A self-described ''tree-hugger for decades,'' she drives her Honda Insight hybrid car or rides the bus when she's not using her bike to get to work.

It's part of her own personal campaign to reduce her carbon footprint. She also powers her home with help from a set of rooftop solar panels, and a geothermal furnace heats and cools it.

The furnace, she adds, even heats her water. Just one more way to reduce emissions, she said.

''Even my 92-year-old mother has a Prius,'' she said. ''So I come by my green credentials genetically.''

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AP Business Writer Emma Vandore in Paris contributed to this report.

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On the Net:

NYCeWheels: http://nycewheels.com

IZIP: http://www.izipusa.com

Ultra Motor: http://www.ultramotor.com/USA