On October 20, 2023, the U.S. Department of Energy (“DOE”) released the National Transmission Needs Study, a triennial report that assesses electric transmission capacity constraints and congestion on a national scale. While similar to previously issued triennial reports, the 2021 Bipartisan Infrastructure Law expanded the study’s scope to also consider anticipated future transmission constraints and congestion. The study assessed needs through 2040 and revealed a pressing need for additional transmission infrastructure to promote reliability in the face of a shifting resource mix, with the largest benefits stemming from increases to interregional transfer capacity.

The study first analyzed trends in transmission investment based on historical data from 2011 to 2020. It found that investment in transmission infrastructure has been steadily declining since 2015. Incremental reliability needs at the local and regional levels were the main drivers of those investments. The study also analyzed historical wholesale market prices to identify where transmission congestion exists. The study revealed that over the past three to five years wholesale electricity prices remained persistently high in the Plains, Midwest, Mid-Atlantic, New York, and California regions. Price analysis demonstrated that the highest benefit of new transmission infrastructure would be found in connecting the middle of the country with its neighboring regions. Specifically, the study determined that the highest value would be achieved by connecting Texas to the Southwest region of the Western Interconnection, and to the Plains and Delta regions in the Eastern Interconnection. Large benefits could also be derived from connecting New York to New England. The study noted a lack of available data for regions outside Regional Transmission Organizations, and cautioned that that should not be interpreted as a lack of transmission infrastructure need.

The study also revealed the drivers of current and expected transmission expansion. Reliability and resiliency will continue to drive expansion to improve operational flexibility, resource sharing, and frequency response as the grid integrates more variable energy resources. Additionally, investments in interregional interconnections will improve resource adequacy in the face of extreme weather events that are likely to affect specific regions over others. The analysis highlights that transmission build-out faces siting and permitting challenges, which may partially (but not totally) be avoided by the strategic siting of generation and transmission.

Finally, the study analyzed six transmission expansion studies to identify potential future need. With moderate load and clean energy growth, the study showed a median 20 percent within-region transmission deployment growth would be needed by 2035. The study also explained that anticipated clean energy growth was likely to be much higher, necessitating a median 64 percent within-region transmission deployment growth by 2035. When coupled with high load growth, the transmission expansion need could grow to 128 percent by the same period. The study revealed that interregional transmission deployment would have to grow by 25, 114, and 412 percent under the same scenarios, respectively. The largest growth in within-region transmission deployment is anticipated in Texas, followed by the Plains, and the Midwest, whereas the largest interregional transmission deployment growth is anticipated between the Delta and Plains, followed by New York and New England, and the Midwest and Plains.

More information about the National Transmission Need Study, including a copy of the report, can be found here.