WestTEC study plans for WECC-wide expansion of transmission system through 2035

At March's Council meeting in Portland, representatives from the Western Transmission Expansion Coalition presented key findings from their new 10-year study examining an expansion of the transmission system in the Western Interconnection, including the Pacific Northwest. (Read presentation | watch video)

The four Northwest states join 10 others, the Canadian provinces of British Columbia and Alberta, as well as a portion of Baja Mexico in comprising the Western Interconnection, also known as the Western Electricity Coordinating Council (WECC) region. Power is generated and traded throughout this broad network on a daily basis, although moving electrons around to meet energy needs has become more of a challenge in recent years due to congestion on the transmission system.

A recent study by Stanford University analyzed the WECC on a peak energy demand day from summer 2025, and found the Northwest's transmission lines had the fourth-highest utilization in the region. The Northwest is not alone in experiencing this congestion, either. Across the West, power systems are experiencing significant load growth, planned resource builds, and large, inter-regional energy transfers, particularly on peak demand days. This combination of factors is helping to drive the need to expand the capacity of the transmission system throughout the WECC.

WestTEC's new 10-year study aims to begin addressing this issue and easing the congestion. It focuses on lines whose capacity is 230-kilovolt and higher in the WECC. The study identified a portfolio of projects that add or upgrade 12,600 miles of the network, at an estimated cost of $60 billion.

Of that total, approximately 9,400 miles represent major planned projects that are under development; WestTEC estimates that almost 20% of these are under construction or are nearing construction. This group includes 73 projects total valued at an estimated $46.6 billion; 8,457 miles are new lines, 553 miles are rebuilds, 348 miles are reconductoring upgrades, and 90 miles are uprates.

Additionally, WestTEC identified a suite of new projects driven by reliability, deliverability, or economic needs:

• Reliability-driven projects included 1,156 miles valued at $6.05 billion; of this total, 947 miles are new projects, 110 miles are rebuilds, and 98 miles are reconductoring upgrades.
• Deliverability projects totaled 1,742 miles valued at $7.24 billion; this included 1,425 miles of new lines, 75 miles of reconductor upgrades, and 242 miles of uprates.
• Economic-driven projects totaled 394 miles of reconductoring upgrades, valued at $391 million.

As the Council develops its Ninth Power Plan in 2026, Power Division staff have relied on the WestTEC analysis to help inform potential transmission availability. Transmission availability is a crucial factor in resource planning for the Northwest's electricity grid.

Western Power Pool has helped lead the WestTEC effort. Chief Operating Officer Ryan Roy told the Council that 10-year study's findings underscore the importance of delivering on planned greenfield lines, while also taking advantage of line upgrades - such as reconductoring, rebuilds, or advanced conductors - that can free up additional capacity in the system at a lower cost per mile.

WestTEC is providing an industry-led, voluntary planning process that has convened a wide range of utilities, power marketers including Bonneville Power Administration, power producers, and transmission and distribution companies, as well as states, technical experts, tribes, environmental groups, trade associations, and others. Power Division staff has also supported this process since it kicked off in 2024. Its next task will be to develop a 20-year plan for the WECC, which it is targeting to release this fall.

"We really wanted to open the tent," Roy said. "It was important that this process be inclusive, and that we get feedback from a broad range of stakeholders. We really wanted to have a broad West-wide footprint. You look at the expected resource additions, load additions, and transmission is lagging significantly behind. We probably should get straight to putting shovels in the ground. We really have to find a way to get these things done."

Roy also put the study's cost estimates in context. He said that the levelized cost of projects outlined in the 10-year study amounts to $5.3 billion annually. That's 4.5% of what customers in the U.S. portion of the WECC spend on electricity each year, or just .1% of the region's gross domestic product. Looking out to the future, the 2035 cost is estimated to be $.004 per kilowatt hour of electricity.