The U.S. Department of Energy (DOE) has advanced three potential National Interest Electric Transmission Corridors (NIETCs) into Phase 3 of its designation process, focusing on areas with critical transmission constraints to enhance grid reliability and reduce consumer costs. The measure is historic—given no NIETCs currently exist despite a decades-long effort to establish them—and it marks significant progress since the concept was redefined under the 2021 Infrastructure Investment and Jobs Act (IIJA).
The DOE’s Dec. 16–announced shortlist pares down 10 preliminary NIETC designations announced in May 2024 under a new four-phase process for designating NIETCs announced in December 2023. Areas that will now initiate the Phase 3 designation process—which involves the public and governmental engagement phase—include:
- Lake Erie-Canada Corridor, including parts of Lake Erie and Pennsylvania
- Southwestern Grid Connector Corridor, including parts of Colorado, New Mexico, and a small portion of western Oklahoma
- Tribal Energy Access Corridor, including central parts of North Dakota, South Dakota, Nebraska, and five Tribal Reservations.
On Monday, the DOE opened a 60-day comment period. “After the close of the public comment window on Feb. 14, 2025, DOE will review comments and create tailored public engagement plans for each potential NIETC,” the agency said. “DOE will determine its obligations under applicable environmental laws in Winter and Spring 2025 and then proceed to conduct any required environmental reviews.” Completion of the evaluation phase during Phase 3 will then allow the agency to release any draft NIETC designation reports and draft environmental documents, though those documents will also require public comment periods.
What Are NIETCs and Why Are They Needed?
While states have long been arbiters of transmission permitting within their boundaries, their patchwork policies for transmission siting, environmental review, and eminent domain has posed a substantial bottleneck for transmission lines crossing state lines. But, assuming even moderate growth and high clean energy growth, 54,500 GW-miles of new transmission will be needed nationwide by 2035—a 64% increase from today’s transmission system—the DOE estimates in its October 2023–issued National Transmission Needs Study. The triennial “state of the grid” report (formerly a “congestion study” which in 2023 included forward-looking attributes) underscored a pressing need for additional transmission infrastructure in nearly all U.S. regions for reliability and resilience.
To address transmission constraints—a longstanding concern that industry has voiced—the Energy Policy Act of 2005 carved out a more significant federal role in certain transmission siting decisions, establishing a “backstop” siting authority for the Federal Energy Regulatory Commission (FERC) that authorized the federal entity to issue permits for the construction or modification of transmission facilities in certain circumstances in areas designated by the Secretary of Energy as NIETCs—areas experiencing or facing capacity constraints.
But while the DOE moved to designate two corridors in the Mid-Atlantic and Southwest NIETCs in 2007, the Ninth Circuit vacated the effort in 2011. Two federal appeals courts in 2009 and 2011, meanwhile, barred FERC and the DOE from leveraging the backstop siting authority. The 2021 IIJA, however, amended Section 216 of the Federal Power Act (FPA) to address issues identified in the decisions. Over the past two years, DOE and FERC proposed new rules to implement their amended authority, which has led to swift action.
On May 8, leveraging its new IIJA authority, the DOE identified 10 preliminary NIETCs. The DOE’s preliminary designations—informed by the findings in DOE’s October 2023–issued National Transmission Needs Study—identified three areas in the East, five in the Central U.S., and one in the West.
But on Monday, the DOE announced that “informed by the substantial comments” received in Phase 2, it had “combined and refined the boundaries of four of the 10 potential NIETCs from Phase 2 to form the boundaries of the three potential corridors proceeding to Phase 3.” It means, the agency said, that the following areas will not proceed as part of the designation process.
- New York-New England
- New York-Mid-Atlantic
- Midwest-Plains
- Mid-Atlantic
- Delta-Plains
- Mountain-Northwest
A Deeper Look at NIETC Designations Moving to Phase 3
The DOE said it “anticipates additional refinement during Phase 3 of the designation process. DOE is focusing on areas where it believes NIETC designation may be most valuable at this time to unlock federal tools to accelerate transmission deployment,” it noted.
Meanwhile, though the DOE identified transmission projects under development in the potential NIETCs, it underscored that “any final NIETC designation is not a route determination for a specific transmission project, and any co-location of a project within a designated NIETC is not a predetermination or indication of the project’s overall eligibility for any DOE financing program.”
Lake Erie-Canada Corridor
Refined from the Mid-Atlantic-Canada proposal in the Phase 2 list, the potential Phase 3 NIETC designation spans northern Pennsylvania and an expanded portion of Lake Erie. The DOE said the corridor has been refined to exclude sensitive areas like Erie Bluffs State Park while broadening offshore coverage to two miles wide. The onshore segment, approximately a quarter-mile in width, provides a narrow but strategically significant route for interregional transmission infrastructure, it suggested.
The corridor is designed to “maintain and improve reliability and resilience and increase clean energy integration, consistent with preliminary findings in Phase 2.” It would provide interregional connections between Canada and PJM, potentially addressing resource adequacy shortfalls within PJM. The interconnection will also facilitate greater clean energy integration, supporting renewable imports and grid stability in one of the nation’s largest power markets, the DOE said.
- Transmission Project Under Development:
- Lake Erie Connector – NextEra Energy Transmission, LLC: A proposed 1,000 MW high-voltage direct current (HVDC) line running beneath Lake Erie to enable efficient electricity exchange between Canada and the U.S., reducing congestion and improving system flexibility.
Southwestern Grid Connector Corridor
Refined from the Mountain-Plain-Southwest and Plains-Southwest corridors in the Phase 2 list, this potential Phase 3 NIETC covers parts of Colorado, New Mexico, and the Oklahoma panhandle. The DOE said the corridor “includes newly added portions of southeastern Colorado and New Mexico” while leveraging existing infrastructure, including transmission line rights-of-way and back-to-back high-voltage direct current (HVDC) substations. With sections ranging from three to fifteen miles wide, the DOE emphasized its role in addressing “congestion, meeting future generation and demand growth, and increasing clean energy integration.”
The corridor serves as a vital connection between the Eastern and Western Interconnections, enabling greater operational flexibility and supporting cross-regional transmission between the Southwest Power Pool (SPP) and WestConnect regions. “The existing transmission lines and substations included in this corridor can help improve reliability and resilience while easing constraints on the grid,” DOE findings suggested.
- Transmission Projects Under Development:
- Heartland Spirit Connector – NextEra Energy Transmission, LLC: A high-voltage line project that will enhance interregional connections between SPP and WestConnect.
- Southline Phase 3 – Grid United: A project aimed at upgrading existing infrastructure to strengthen energy transfer capacity across regional seams.
Tribal Energy Access Corridor
The Tribal Energy Access Corridor, refined from the Northern Plains corridor in the Phase 2 list, spans central North Dakota, South Dakota, Nebraska, and five Tribal reservations: Cheyenne River, Pine Ridge, Rosebud, Standing Rock, and Yankton. The DOE noted that the corridor “connects multiple Tribal reservations to existing or under-development higher-voltage transmission lines” and follows existing rights-of-way for most of its path, which ranges from two to fifteen miles wide.
According to the DOE, the corridor is specifically designed to “alleviate congestion and reduce consumer costs, increase clean energy integration, and meet future generation and demand growth.” It also highlights the unique opportunity to support Tribal energy development. “By addressing a lack of extra-high-voltage transmission infrastructure, this corridor could facilitate Tribal energy and economic development, providing much-needed opportunities for clean energy projects and investment,” the DOE said.
- Transmission Project Under Development:
- TRIBES Project – A partnership led by the Western Area Power Administration, Basin Electric Power Cooperative, and Oceti Sakowin Power Authority (along with member Tribes, IBEW Local 1250, and Steelhead Americas): Focused on building out bulk electric supply infrastructure to improve grid access, integrate renewables, and create economic opportunities for Tribal communities.
—Sonal Patel is a POWER senior editor (@sonalcpatel, @POWERmagazine).
