More than 43,000 miles of new transmission lines needed in the U.S. by 2040, DOE study says
Energize Weekly, March 15, 2023
The United States is projected to need more than 47,300 gigawatt-miles of new transmission lines by 2040 – in some cases they will be needed as soon as 2030, according to a draft U.S. Department of Energy report.
“The electric grid continues to face challenges from aging infrastructure and insufficient transmission capacity,” the draft, which was made available for public comment, said. “The need for transmission growth is even greater in future scenarios that have high load and high clean energy assumptions.”
The study is premised on the need to accommodate clean energy load growth and to resolve load and cost discrepancies within regional systems, such as the Midcontinent System Operator (MISO) or the Southwest Power Pool (SPP).
These cost differences become most acute to periods of high demand and disruptions such as winter storms and hurricanes.
“Several regions of the country have experienced consistent electricity price differentials over the past 3–5 years,” the report said. “Extreme conditions and high-value periods play an outsized role in the value of transmission, with 50 percent of transmission congestion value coming from only 5 percent of hours.”
The timing for new transmission varies from region to region. Major additions will be needed as soon as 2030 in the Plains, Midwest, and Texas to meet demand, while the Mountain, Mid-Atlantic, and Southeast regions will experience heightened demand by 2040.
The largest growth in interregional transfer capacity would be needed between the Plains and Midwest, the Midwest and the Mid-Atlantic, and between New York and New England.
Increased transmission capacity will improve grid reliability, resilience, and resource adequacy as well as enhanced renewable resource integration and access to clean energy, the DOE said.
It will also buttress electrification efforts and reduced congestion and curtailment.
A focus of the report was the need to improve transmission out of the central U.S. “Large amounts of low-cost generation potential exist in the middle of the country and accessing this generation through increased transmission is cost effective for neighboring regions,” the report said.
The transmission needs vary region to region. MISO North, which covers North Dakota, South Dakota, Minnesota, and Iowa currently experiences higher congestion than other MISO regions. Congestion in this region doubled between 2019 and 2020 and is continuing to increase.
Transfer limits between MISO Central – Kentucky, Missouri, Illinois, Indiana, Wisconsin, and Michigan – and MISO South – Arkansas, Mississippi, Louisiana, and Texas – are binding most of the year, contributing to insecure operations during extreme events in both regions.
Overall, the study projects a need in MISO of between 10,000 gigawatt-miles and 14,900 gigawatt-miles of new transmission by 2035 to meet moderate load growth and a “high clean energy future.”
The vulnerability of the Texas grid, operated by the Electricity Reliability Council of Texas (ERCOT), was highlighted during a severe winter storm in February 2021 when the grid operator was forced to shed 20,000 megawatts of firm load – leading to rolling blackouts – while it was unable to import additional capacity above its 1,000 MW transfer limit.
The system, the DOE noted, is also vulnerable to outages from hurricanes, such as the ones caused by Hurricane Laura in 2020 and Hurricane Ida in 2021.
The study projects the need for between 6,800 and 9,400 gigawatt-miles of new transmission for the ERCOT grid, with the median 9,000 gigawatt-miles representing a 140 percent increase compared to the 2020 system. Those additions should be in place by 2035.
The SPP region was also unable to import additional capacity during the February 2021 cold weather event, negatively impacting resource adequacy.
In addition, the Southeast Missouri and Southern Oklahoma area of the SPP grid have experienced consistently high prices – about $20 a megawatt-hour more – for at least the past two to three years due to transmission constraints.
The Pacific Northwest, California, Arizona, and the Mountain West collectively need nearly 15 gigawatts of transfer capacity among the regions.
“This study prescribes no particular solutions to issues faced by the Nation’s power sector,” the report said. “Rather, it establishes findings of need in order for industry and the public to suggest best possible solutions for alleviating them in a timely manner.”