RENO, Nev. — Out-of-state wind integration, merchant transmission development and the WestTEC planning effort are all factors influencing CAISO’s interregional transmission planning.

Neil Millar, CAISO’s vice president of infrastructure and operations planning, gave a briefing on the ISO’s West-wide transmission activities during the June 18 meeting of the Western Energy Markets Governing Body.

As a starting point for interregional transmission planning, CAISO uses its regional transmission planning process, Millar said. The CAISO Board of Governors on May 22 approved the 2024/25 transmission plan, which includes 31 projects valued at a total of $4.8 billion. (See CAISO Approves $4.8B Transmission Plan to Support 76 GW of New Capacity.)

CAISO’s previous three transmission plans included $5.8 billion in projects on average, which largely were policy-driven projects to support access to resource basins, Millar said. But projects in the 2024/25 plan are focused mainly on reliability in the face of surging load growth.

Millar said last year’s transmission plan was based on load growth of about 1% per year, while the load growth in this year’s plan was about 1.6%. CAISO now is looking at a load growth rate of about 2.5% for next year’s plan.

“The increased rate of load growth reflected in the most recent load forecast associated with building and other electrification, data center growth and transportation electrification results in significant reliability-driven needs in this year’s transmission plan,” the 2024/25 plan stated.

Out-of-state Wind

Accessing out-of-state wind continues to be a focus for the ISO. Millar said CAISO’s base case scenarios call for seeking more than 5,500 MW of Wyoming and Idaho wind resources and more than 3,600 MW of New Mexico wind.

He said CAISO is working with its neighbors to explore potential coordination on specific projects or to leverage merchant projects that might be moving forward.

And supporting the Western Transmission Expansion Coalition (WestTEC) effort is a priority for CAISO, according to Millar.

The WestTEC effort, jointly facilitated by the Western Power Pool and WECC, will address long-term interregional transmission needs across the Western Interconnection. The goal is to produce transmission portfolios for 10- and 20-year planning horizons.

WestTEC expects to release its initial 10-year horizon report in August, according to a June 12 presentation to the group’s Regional Engagement Committee. The group projects that the 20-year horizon report and the final 10-year report will be completed by September 2026. (See WestTEC Tx Study on Track Despite Delays.)

For Millar, the key advantage of WestTEC is that it will create an “actionable” plan. He said it’s one of the first studies based on extensive input from load-serving entities about their resource plans, particularly in its 10-year horizon.

CAISO will use the information to help identify opportunities it will emphasize, either by itself or in collaboration with other entities.

“At this point, I’m not in a position to tell you which projects we’re throwing our weight behind, because we are looking to see what falls out from the WestTEC effort first before we move to that next stage,” Millar said.