PEOPLE concerned about Americans' dependence on oil, a significant amount of which comes from hostile sources, have great hopes for wind farms.

The industry is growing fast, despite opposition from those who object to what wind farms do to the scenery.

But wind power can contribute only so much to energy independence. Its role should be appreciated, but not oversold.

Scott Malone of Reuters reported recently on the scramble to finish the largest wind farm in the northeastern United States, an array of 185 windmills about 300 miles northwest of New York City. The project had hit a snag -- difficulty obtaining parts.

Major wind turbine manufacturers like Vestas Wind Systems of Denmark, Siemens AG, and General Electric are scrambling to keep up with demand. Siemens has announced plans to open a factory in Iowa to make turbine blades.

Siemens has orders for turbines capable of generating 600 megawatts of electricity, and expects to double its volume in the United States in the next three years. GE said it has as much business as it can handle in 2006 and 2007, and is taking orders for 2008.

Victor Abate, vice president of renewable energy at GE, said the company expects to ship 2,000 turbines this year and record $3.4 billion worth of sales. He expects a 30 percent increase in 2007.

But as hot as sales are, some question how large a contribution wind power can make.

Wind farms now generate about 0.5 percent of the electricity produced in the United States, and the American Wind Energy Association thinks that can be raised to 20 percent.

But windmills need wind to generate power, and sometimes they don't get it.

"It can't be counted on for reliable supply," said Paul Flemming, director of power and gas at Energy Security Analysis Inc., a research firm.

A more realistic expectation, some experts say, is that wind could supply 6 percent to 10 percent of the nation's need for electrical power.

That would be a helpful contribution, but it will fall short of a panacea.