State of the Interconnection 2025
Transfer Capability
Transfer capability is an important measure of the system's ability to move power from resources to load. The Interregional Transfer Capability Study (ITCS) showed some potential energy concerns under extreme weather conditions for Northern California and Alberta and recommended prudent transfer capability increases or other actions to address the concerns.
Coordinated Planning
WECC has asserted that in order to identify and meet the challenges of the future, entities need to engage in coordinated transmission and resource planning. WECC, the ERO Enterprise, and FERC have stated the importance of coordinated, wide-area planning, and entities like the California ISO and partnerships like WestTEC are already performing coordinated planning.
Interregional Transfer Capability Study
In 2023, as a result of the Fiscal Responsibility Act of 2023, WECC and other members of the Electric Reliability Organization (ERO) Enterprise began work on the ITCS to examine the ability to transfer electricity between regions of the country during extreme weather or unexpected outages. The ITCS was filed with FERC in November 2024, and the supplemental Canadian analysis was filed in April 2025. The study broke new ground in evaluating transmission across the continent, including potential transmission additions to bolster transfer capability.
ITCS Highlights
General Findings
- In addition to limited transfer capability between the interconnections, transfer capability is generally lower in the Mountain States, Great Plains, Southeast, and the Northeast regions. Transfer capability is greatest in the West Coast, Great Lakes, and Mid-Atlantic areas.
- The vulnerability of the North American power system to extreme weather was evident in all twelve of the years studied, with wide variation in potential impact and import capability needs across regions.
- The study identified both recommended prudent transfer capability increases and alternatives to addressing potential energy inadequacy, including resource development, transmission enhancement, and demand-side management initiatives.
- The study recommends prudent transfer capability increases between all interconnections.
The West
- Under large-scale heat events—such as the 2020 heat event—the California North study region experienced energy adequacy challenges in the analysis. The study recommends prudent transfer capability increases between the California North and Wasatch Front study regions.
- Alberta experienced energy adequacy challenges in the study. Additional transfer capability with Saskatchewan could alleviate the deficiencies, as could strengthening existing connections to the U.S. or British Columbia.
- The study identified no other prudent additions to transfer capability within the Western Interconnection.
20-Year System Planning
20-Year Study
In 2022, WECC identified a need for transmission planning beyond the traditional 10-year planning horizon. In 2024, WECC released the 20-year Transmission Trends Assessment, which is WECC's first work to identify risks in the 20-year future. The analysis evaluated four 20-year scenarios and compared the results to identify trends in transmission use and energy flows. The report shares key lessons learned, including:
- Improvements to battery modeling are needed to more accurately evaluate the effect of battery charging and discharging during peak load times.
- To make up for the lack of 20-year system planning information, WECC created a simplified capacity expansion dataset. More detailed evaluation of risks in the 20-year future will require additional information from planning entities in the 20-year time frame.
- Most subregions required increased imports during both the extreme cold and extreme heat events.
- Transmission path utilization increased on several paths and in some cases, flow on transmission paths reversed directions.
Order 1920
In May 2024, FERC adopted Order 1920, which addresses the need for longer-term transmission planning by requiring transmission planners to conduct 20-year planning. Following its adoption, states, utility regulators, and clean energy groups opposed the order based on concerns that the rule undermined state authority in transmission planning and could lead to unfair rates. After a rehearing, FERC revised the rule to give state regulators a larger role in the transmission planning and cost allocation processes. The order encourages and in some instances requires increased collaboration with state regulators, particularly on the matter of cost allocation. The order requires transmission planners to:
- Conduct regional transmission planning at least every five years, using a 20-year planning horizon.
- Develop at least three plausible scenarios considering various factors like resource mix, decarbonization goals, and technology trends.
- Consider and quantify a comprehensive set of benefits, including reliability, cost, and environmental factors.
WestTEC
The Western Power Pool launched the Western Transmission Expansion Coalition (WestTEC) in fall 2023. It is an industry-led, West-wide effort to develop a transmission plan that supports the needs of the future electric grid and identifies benefits such as enhanced reliability and improved economic efficiency.
The plan consists of two components. The first looks at a 10-year planning horizon and is focused on feasible solutions such as grid-enhancing technologies and the use of existing rights-of-way. This report is expected to be completed in summer 2025.
The second component examines options 20 years in the future and focuses more on portfolio solutions, or new transmission projects that will be more complex and take longer to build. This report is expected be completed in early 2027, providing an actionable plan based on strategic, long-term analysis of the entire Western Interconnection.
Coordinated Transmission & Resource Planning
Coordinated planning of transmission and resources is critical for understanding how the interconnection may be affected by and should plan to overcome increasingly complex reliability risks. This need is being discussed in several arenas:
- Concerns about both resource adequacy and transmission availability during events like the recent intense, prolonged, and widespread heatwaves led WECC to include the lack of coordinated planning in its top priority reliability risks in 2024.
- The ITCS recommends that system planning work holistically to evaluate transmission and resources over a wide area to assess whether resources in neighboring areas are available during times of need.
- In Order 1920, FERC asked transmission planners to incorporate “state-approved utility integrated resource plans and entities’ expected supply obligations” when developing the scenarios they use to identify long-term transmission needs and regional transmission facilities needed to meet those needs.
Transmission Project Highlights in 2024
SunZia: 525-kV DC line spanning 550 miles from central New Mexico to south-central Arizona with the capacity to transport 3,000 MW of wind energy from a 3,500 MW facility in New Mexico. Expected to be operational by 2026.
Power Pathway: Five-segment project covering 550 miles across 12 counties, mainly in eastern Colorado. The first segments are expected to be in service by 2025, with the remaining work completed in 2026 and 2027.
Energy Gateway South: 416-mile, 500-kV line connecting wind farms in Wyoming to southern Utah. It was completed in November 2024.
Energy Gateway West: 1,000 miles of new high-voltage transmission lines in Wyoming and Idaho. It consists of three segments, one of which was completed in 2020, another in November 2024, and the third is scheduled to be in service in 2034 at the earliest.
Boardman to Hemingway: Proposed 500-kV line running approximately 290 miles from eastern Oregon to southwestern Idaho. Construction is expected to begin in 2025 and finish in 2027.
TransWest Express: Construction began in 2023 on the 732-mile line running from a wind facility under construction in Wyoming, through Colorado and Utah, to near Las Vegas. The power will be available for use in Arizona, southern California, and Nevada when the line is completed in 2029.
Greenlink West: 525-kV line spanning 350 miles from Las Vegas, Nevada, to Yerington, Nevada. Construction is expected to begin in early 2025, with the line in service by spring 2027.
Greenlink North: 525-kV line running from Ely, Nevada, to Yerington, Nevada. Expected to be in service in late 2028.
Cross-Tie: Proposed 500-kV line spanning 214 miles through Utah and Nevada to relieve congestion on other transmission lines in the region and increase the ability of several states to import and export renewable energy.
SWIP-North: 500-kV line covering 285 miles from southern Idaho to Ely, Nevada. It is the final link in a transmission corridor that will enable the bidirectional flow of about 2 GW between the Desert Southwest and Pacific Northwest. Construction is expected to begin in 2025 and completed in 2027. In 2024, it was selected as a participant in DOE’s Transmission Facilitation Program.
Southline Transmission Project: 278-mile line connecting the existing transmission systems of the metro areas in El Paso, Texas, and Tucson, Arizona. Construction is expected to begin in 2025, with its two phases complete in 2027 and 2028. In 2024, it was selected as a participant in DOE’s Transmission Facilitation Program.
Bonneville Power Administration: In October, BPA announced plans for 13 transmission, substation, and line projects. The projects include a 500-kV line from northern Oregon to Nevada. The projects are in the early stages of development and will not affect work on several transmission projects BPA announced in summer 2023.
Boardman to Hemingway project breaks ground this year
In the works since the mid-2000s, the Boardman to Hemingway (B2H) transmission project is on track to break ground this year.
B2H is a proposed 290-mile, 500-kV transmission line that will run from a substation near Boardman, Oregon, to the Hemingway Substation near Melba, Idaho. The line is co-owned by Idaho Power and PacifiCorp. It will connect the winter-peaking Pacific Northwest and summer-peaking Intermountain West to provide customers in both areas reciprocal benefits. In the winter, when hydropower generation is low, Pacific Northwest customers will be able to use power from wind facilities in the Intermountain West. During summer demand peaks, customers in the Intermountain West will benefit from hydropower and other resources in the Pacific Northwest.
The project first appeared in Idaho Power’s Integrated Resource Plan in 2006. Permitting issues have been the primary source of delay. Idaho Power is the lead developer of the project, which spans more than 100 miles of federal land, requiring approval from the Bureau of Land Management, U.S. Forest Service, U.S. Navy, and the Bureau of Reclamation. It also covers state land in Idaho and Oregon, as well as tribal and private land. As of December 2024, the project was awaiting final approval of federal, state, and local permits. There is also an appeal pending before the Oregon Supreme Court related to a site certificate approved in summer 2024.
According to Idaho Power, B2H is crucial to meeting soaring demand and achieving its goal of 100% clean energy by 2045. The project is on track to break ground this spring and to be in operation in 2027.
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