That is a symptom of a broad national problem. Expansive dreams about renewable energy, like Al Gore’s hope of replacing all fossil fuels in a decade, are bumping up against the reality of a power grid that cannot handle the new demands. The dirty secret of clean energy is that while generating it is getting easier, moving it to market is not.

The grid today, according to experts, is a system conceived 100 years ago to let utilities prop each other up, reducing blackouts and sharing power in small regions. It resembles a network of streets, avenues and country roads. “We need an interstate transmission superhighway system,” said Suedeen G. Kelly, a member of the Federal Energy Regulatory Commission. While the US today gets barely 1 per cent of its electricity from wind turbines, many experts are starting to think that figure could hit 20 per cent.

Achieving that would require moving large amounts of power over long distances, from the windy, lightly populated plains in the middle of the country to the coasts where many people live. Builders are also contemplating immense solar-power stations in the nation’s deserts that would pose the same transmission problems.

The grid’s limitations are putting a damper on such projects. Gabriel Alonso, chief development officer of Horizon Wind Energy, the company that operates Maple Ridge, said in parts of Wyoming, a turbine could make 50 percent more electricity than the identical model built in New York or Texas.

“The windiest sites have not been built, because there is no way to move that electricity from there to the load centres,” he said.

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, NY, 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.