Contextualizing Electric Transmission Permitting: Data from 2010 to 2020

The report analyzes transmission development between 2010 and 2020, finding that while projects requiring an Environmental Impact Statement (EIS) represent only 3.5% of new lines, they account for 26% of new line miles. These projects are typically longer, more likely to be driven by renewable generation interconnection, and more likely to cross state or international borders. The average EIS review timeline is 4.3 years, with a moderate correlation between line length and review duration. The authors argue that these long and unpredictable timelines pose a challenge to future grid reliability and decarbonization goals, especially as federal funding and authority increase the likelihood of projects triggering federal reviews.

• Projects requiring an Environmental Impact Statement (EIS) represent a small fraction of the total number of new transmission lines but a significant portion of total mileage. Specifically, 33 projects accounted for 3.5% of all new transmission lines but 26% of all new line miles added to the bulk power system between 2010 and 2020.
• Transmission lines built to interconnect renewable generation are more likely to require an EIS and are significantly longer than other project types. They accounted for 61% of lines with an EIS, compared to 26% of all new lines in the bulk power system. The average length for renewable interconnection projects requiring an EIS was 277 miles, compared to an average of 51 miles for all renewable interconnection lines.
• The average timeline for an EIS review from the Notice of Intent (NOI) to the Record of Decision (ROD) was 4.3 years, with a median of 3.7 years and a range between 1 and 11 years.
• There is a moderate positive correlation (Pearson correlation coefficient of 0.41) between the length of a transmission line and the time required for its EIS review, with every additional 100 miles of line length correlating to a nearly 5-month increase in review time.
• EIS requirements disproportionately affect interstate projects and those in the Western U.S. While only 5.5% of all new lines crossed state or international borders, 45% of lines requiring an EIS did. Additionally, 64% of projects requiring an EIS were located in the non-RTO West or the California Independent System Operator (CAISO) region, despite that region accounting for only 12% of all new lines.
• The most common triggers for a NEPA EIS review were projects crossing federal land or having federal involvement in project funding.

APA

Manitius, N., Cavert, J., & Kelly, C. (2024). Contextualizing Electric Transmission Permitting: Data from 2010 to 2020. Clean Air Task Force. https://cdn.catf.us/wp-content/uploads/2024/03/03143914/NEPA-Transmission-Report.pdf

Chicago

Manitius, Natalie, Johan Cavert, and Casey Kelly. Contextualizing Electric Transmission Permitting: Data from 2010 to 2020. Clean Air Task Force, 2024. https://cdn.catf.us/wp-content/uploads/2024/03/03143914/NEPA-Transmission-Report.pdf.

Wikipedia

{{cite report |last1=Manitius |first1=Natalie |last2=Cavert |first2=Johan |last3=Kelly |first3=Casey |title=Contextualizing Electric Transmission Permitting: Data from 2010 to 2020 |publisher=Clean Air Task Force |date=March 2024 |url=https://cdn.catf.us/wp-content/uploads/2024/03/03143914/NEPA-Transmission-Report.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{manitius2024contextualizing, author = {Manitius, Natalie and Cavert, Johan and Kelly, Casey}, title = {{Contextualizing Electric Transmission Permitting: Data from 2010 to 2020}}, institution = {Clean Air Task Force}, year = {2024}, month = mar, url = {https://cdn.catf.us/wp-content/uploads/2024/03/03143914/NEPA-Transmission-Report.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }