It could come down to the wire — literally. US President Joe Biden’s ambitious climate agenda hinges on transcontinental clean electric grid, but the ability of his administration to accelerate the herculean construction project required to build such a vast network of new power lines remains under a looming question mark.

“Limited electric transmission capacity is the biggest barrier to clean energy growth and US emission reductions because the large wind and solar farms can’t get connected to the grid,” said Rob Gramlich, president of consulting firm Grid Strategies.