In May, the California Independent System Operator (CAISO) Board of Governors approved the “ISO’s 2025-2026 Transmission Plan,” recommending 38 infrastructure projects to accommodate rising electricity demand and to support the state’s energy goals.

More than half the projects (and more than half of the $6.7 billion estimated costs) are driven by forecasted load growth.

Most of the remaining projects are needed to access resource development basins identified by the California Public Utilities Commission (CPUC) and to serve load and meet state reliability and greenhouse gas reduction goals.

Initial draft estimates released in April projected $7 billion in upgrades, but updated cost assumptions have reduced the total projected costs to $6.7 billion at full buildout over the next decade.

“We are constantly striving to find ways to meet system needs in the most affordable way possible,” said Neil Millar, the ISO’s vice president, Transmission Planning and Infrastructure Development. “This year’s plan does that in a number of different ways while also making sure we have the right infrastructure in place to accommodate all of the new resources that are being added to the system.”

This year’s plan includes 12 reconductoring projects that increase transmission capacity without having to build new transmission from scratch. Three of these will employ advanced conductors, which are one of a suite of grid-enhancing-technologies (GETs), that the ISO routinely considers in its planning efforts.

Another hallmark of the ISO’s planning process is ongoing analysis of grid congestion, which can result in dispatching higher-priced generation to serve load when transmission limitations restrict access to lower-cost power. “Planners use production cost modeling to compare the cost of new infrastructure against the customer savings from reducing congestion,” said CAISO. “This helps determine when it is more economical to reinforce the system rather than continue operating with recurring bottlenecks.”

The plan is based on the California Energy Commission’s (CEC’s) projections showing that California’s load will grow by 15 gigawatts (GW) by 2035 and 20 GW by 2040, while the installed resource capacity, provided by the CPUC, will need to increase by more than 74 GW and 107 GW within those same timelines.

As described in the CEC’s load forecast, the increasing demand is being driven by building and transportation electrification, manufacturing, and large loads, including data centers.