In the Netherlands, a third of the money spent on bicycles last year went to electric-powered models. Industry experts predict similar growth elsewhere in Europe, especially in Germany, France and Italy, as rising interest in cycling coincides with an aging population. India had virtually no sales until two years ago, but its nascent market is fast expanding and could eclipse Europe’s in the next year.

Image Roger Phillips, 78, uses an electric bicycle in Manhattan, although they are not officially permitted on New York streets. Credit... Nicole Bengiveno/The New York Times

“The growth has been tremendous in the last two years,” said Naveen Munjal, managing director of Hero Electric, a division of India’s largest bicycle and motorcycle maker. He expects sales at Hero to increase to 250,000 electric bikes in 2012, from 100,000 in 2009.

While the American market has been modest  about 200,000 bikes sold last year, by some estimates  interest is rising, said Jay Townley, a bicycle industry consultant. Best Buy began selling electric bicycles in June at 19 stores in San Francisco, Los Angeles and Portland, Ore. Trek, a manufacturer based in Wisconsin, recently began selling a bike created by Gary Fisher, a prominent bicycle designer.

“Electric-assisted bicycles will change how people think about bikes in urban areas,” predicted Mr. Chiu of San Francisco, who has been riding a prototype of the Trek bike since the summer.

Improvements in technology are resulting in lighter designs that appeal to older cyclists. “Now you’ve got a product you can present to a baby boomer,” Mr. Townley said.

New York City’s largest electric bike store, NYCeWheels, opened in 2001, and in the last few years, business has been growing, said Bert Cebular, the owner. In Chinatown, electric bikes are showing up on nearly every corner and several shops have recently appeared, selling bikes imported from Chinese factories.

As the global market develops, two types of electric bikes are emerging. One is similar to a standard bicycle with pedals, but it has an electric motor that engages on command or when the cyclist pedals. These are the most popular type in the United States and Europe, with many people using the electric motor mainly for help in wind or on steep hills.