The basic problem is that many transmission lines, and the connections between them, are simply too small for the amount of power companies would like to squeeze through them. The difficulty is most acute for long-distance transmission, but shows up at times even over distances of a few hundred miles.

Transmission lines carrying power away from the Maple Ridge farm, near Lowville, N.Y., have sometimes become so congested that the company’s only choice is to shut down — or pay fees for the privilege of continuing to pump power into the lines.

Politicians in Washington have long known about the grid’s limitations but have made scant headway in solving them. They are reluctant to trample the prerogatives of state governments, which have traditionally exercised authority over the grid and have little incentive to push improvements that would benefit neighboring states.

In Texas, T. Boone Pickens, the oilman building the world’s largest wind farm, plans to tackle the grid problem by using a right of way he is developing for water pipelines for a 250-mile transmission line from the Panhandle to the Dallas market. He has testified in Congress that Texas policy is especially favorable for such a project and that other wind developers cannot be expected to match his efforts.

“If you want to do it on a national scale, where the transmission line distances will be much longer, and utility regulations are different, Congress must act,” he said on Capitol Hill.

Enthusiasm for wind energy is running at fever pitch these days, with bold plans on the drawing boards, like Mayor Michael Bloomberg’s notion of dotting New York City with turbines. Companies are even reviving ideas of storing wind-generated energy using compressed air or spinning flywheels.

Yet experts say that without a solution to the grid problem, effective use of wind power on a wide scale is likely to remain a dream.