State of the Interconnection 2026
Transfer Capability
Transfer capability is an important measure of the system's ability to move power to where it is needed. The Interregional Transfer Capability Study (ITCS) found that the ability to transfer an additional 35 GW across regions would mitigate reliability risks. The study also identified barriers to transmission development, including siting and permitting challenges, and recommended a broad set of solutions in addressing risks to reliability.
Coordinated Planning
Western Transmission Expansion Coalition's (WestTEC) 10-year transmission study found that the interconnection needs significant expansion and upgrades to meet load growth over the next decade. About two-thirds of the recommended improvements are already planned. The study also determined that coordinated action is needed among western states, utilities, developers, and regional partners to develop the most efficient and effective transmission system.
Interregional Transfer Capability Study
In February 2026, FERC sent a report to Congress on the Interregional Transfer Capability Study (ITCS). The study, completed by NERC in collaboration with WECC and the other members of the Electric Reliability Organization Enterprise, analyzed how electricity moves between regions, identified potential opportunities to strengthen connections between neighboring regions, and examined ways to enhance reliability by increasing interregional transfer capabilities. Among the findings —
- Energy deficiencies were identified in all 12 weather years studied.
- The import capability needed during extreme conditions varied significantly across the country.
- An additional 35 GW of transfer capability across the U.S. was identified as being beneficial for reliability, about 1.1 GW in the Western Interconnection.
The ITCS was mandated by Congress in 2023 through the Fiscal Responsibility Act. It called on NERC to complete the study and submit it to FERC for public comment, followed by the report summarizing the findings and recommended statutory changes, if needed. FERC's report declined to provide recommendations and commended the ITCS as “valuable” and “an advancement in existing transfer analysis and modeling processes.”
WestTEC Publishes 10-Year Transmission Study
The Western Transmission Expansion Coalition, or WestTEC, released its 10-Year Horizon Study in early 2026, finding that the West needs to add more than 126,000 miles of new transmission lines over the coming decade, at an estimated cost of $60 billion, to maintain reliability amid rising demand while addressing aging infrastructure and integrating new generation. WestTEC’s 20-year study is expected to be complete later this year.
WestTEC is an interregional planning effort to develop a transmission study that instructs transmission development throughout the West. Western Power Pool is leading the effort with an emphasis on collaboration with a range of stakeholders from industry, Tribes, and the states. More than 70 organizations from across the Western Interconnection have taken part in the coalition since its inception in 2023.
Transmission Project Highlights in 2025
Here is a look at significant transmission projects in the Western Interconnection that progressed or were completed in 2025 or early 2026:
SunZia: This 550-mile, 525-kV, direct current transmission line runs from central New Mexico to south-central Arizona, connecting 3 GW of wind generation. It went into operation in April 2026.
Energy Gateway West: 1,000 miles of new high-voltage transmission lines in Wyoming and Idaho. The project consists of three segments, with two in service and the third scheduled to be on-line in 2034 at the earliest.
Boardman to Hemingway: Construction started in Oregon in August 2025 and is scheduled to be completed in late 2027 on this 500-kV line that will run nearly 300 miles across eastern Oregon and southwest Idaho.
TransWest Express: Construction continued in 2025 on this 732-mile interregional line that will link the three planning regions in the Western Interconnection. The power will be available for use in Arizona, southern California, and Nevada when the line is completed in 2029.
Greenlink West: Construction began in 2025. The new line will run nearly 500 miles, connecting an existing substation near Las Vegas to a substation in northern Nevada.
Greenlink North: 525-kV line in the permitting stages, with construction expected to start in 2027. When complete, it will run 235 miles across Nevada.
Cross-Tie: Proposed 500-kV line would run 217 miles from Utah to Nevada. It received approval from the Bureau of Land Management and Forest Service in late 2025 and is expected to be in service in 2030.
SWIP-North: Construction is expected to begin in 2026 on SWIP-North, the last segment of the larger SWIP project that began decades ago. SWIP-North will run 285 miles from eastern Nevada to south-central Idaho.
Southline Transmission Project: This 280-mile line will connect existing transmission facilities in Arizona and New Mexico in two phases. Construction is expected to begin in 2026, with both phases complete by 2029.
RioSol: Construction is expected to start in 2026 on this 550-mile line that will run from central New Mexico to south-central Arizona.
North Plains Connector: In the permitting stages, this project would run 420 miles from Montana to North Dakota, connecting the Western and Eastern Interconnections.
Ready Wyoming: A 260-mile expansion of the transmission network across the state that was completed in 2025.
BPA continues to develop transmission network
In 2023 and 2024, Bonneville Power Administration announced over 20 new transmission line and substation projects, totaling roughly $6.6 billion in estimated costs, to help improve transmission capacity and reliability throughout the Northwest.
These projects are referred to as the Grid Expansion and Reinforcement Portfolio (GERP) to reflect the expanded scope and purpose of the work. They are split into two portfolios: GERP 1.0 and 2.0
GERP 1.0 consists of 10 projects at a projected cost of $2.6 billion. Mostly upgrades to existing facilities, these projects are expected to support regional load growth, reliability needs, and commercial transmission service and interconnection requests. Most of these projects were in the scoping or design phase in early 2026, and are expected to be in service in 2032.
GERP 2.0 consists of 13 projects at a projected cost of $3.9 billion. These projects would also support regional load growth, reliability needs, and commercial transmission and interconnection service requests. Most of these projects are expected to begin the scoping phase in 2026, and to be in service in the mid-2030s.
View an interactive map of the GERP projects.
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