The U.S. Department of Energy’s latest National Transmission Needs study, released in October, says the United States needs about 47,000 GW-miles of new high-voltage transmission capacity by 2035 under a moderate load-growth, high clean-energy scenario. That represents a 57% increase from present system capacity, according to DOE.
Yet the pace of transmission expansion remains slow, with just 386 miles of new high-voltage lines built in 2021, according to the American Clean Power Association. Individual projects can take 10 to 20 years to move from concept to interconnection; the 3-GW, 732-mile TransWest Express line is expected to finish construction in 2027, 22 years after initial planning began, per Wood Mackenzie.
