The California Independent System Operator (ISO) Board of Governors has approved the 2024–2025 Transmission Plan, which outlines 31 proposed infrastructure projects designed to accommodate projected increases in electricity demand and evolving grid requirements across the state.
Of the 31 proposed projects, 28 are aimed at addressing anticipated load growth — particularly in the Greater San Francisco Bay Area — driven by increasing electrification and electric vehicle usage. The remaining three projects are intended to support renewable energy integration in accordance with state energy portfolio targets developed by the California Public Utilities Commission (CPUC).
The total estimated cost of the projects is approximately $4.8 billion, with full implementation expected over a 10- to 15-year period.
Among the approved initiatives are five reconductoring projects that involve upgrading existing lines with advanced conductors. These projects are intended to increase transmission capacity without the need for constructing entirely new lines. The use of grid-enhancing technologies such as these has been part of the ISO’s planning strategy in recent years.
Transmission planning is one of the ISO’s core responsibilities and is conducted annually based on system reliability and policy goals. The 2024–2025 plan was developed in coordination with the CPUC, the California Energy Commission, and other regulatory agencies. This year’s plan extends the planning horizon from 10 years to 15 years, aligning with legislation passed in 2022 that allows for more time for project approval, permitting, and construction.
According to data provided to the ISO in 2024, California is projected to require over 76 gigawatts (GW) of additional capacity by 2039. The plan also reflects updated projections of load growth, with the state’s year-over-year peak demand growth rate forecast to increase from 0.99% to 1.53%. In the Greater San Francisco Bay Area, the load growth is expected to rise from 1.22% to 2.14%, primarily due to electrification in the transportation and building sectors, as well as the expected expansion of data centers.
In developing the plan, the ISO reviewed a wide range of options to identify the most cost-effective transmission solutions. These included potential upgrades, energy storage, and other grid technologies.
Key projects approved in the plan include:
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Greater Bay Area 500-kV Transmission Reinforcement – a new 500-kilovolt line to serve the southern Bay Area;
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San Jose B – Northern Receiving Station 230 kV Line – a new 230-kilovolt line in San Jose;
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South Bay Reinforcement – reconductoring and reconfiguration of five 115-kV lines in San Jose;
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North Oakland Reinforcement – integration of two new 115-kV sources and upgrades to existing infrastructure;
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South Oakland Reinforcement – reconductoring of three 115-kV lines;
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Additional smaller-scale upgrades to improve local supply and resource access.
The final plan follows a stakeholder engagement process that included public meetings and opportunities for feedback.
