Ramping up wind and solar power could provide the nation with promising sources of alternative energy, but the U.S.’s existing electricity grid may not be able to handle it.

That’s the word from a new report from the North American Electric Reliability Corporation, released on Monday (Nov. 10) and discussed in a story on the same day in The New York Times.

Alternative energy initiatives “would impose new demands on a transmission system that was never designed for large power transfers over extremely large distances,” reporter Matthew L. Wald wrote of the report’s warning.

“We are concerned that, when viewed from a continent-wide perspective, current climate initiatives do not adequately address key reliability objectives, particularly the need for a strong and robust transmission system,” Rick Sergel, president and chief executive of NERC, said on the organization’s website.

Energy experts have spoken widely of the need for new grid infrastructure to handle increasing loads from wind and solar power plants. That challenge must be met if alternative energy sources are ever to make substantial contributions to the nation’s energy supply.