CAISO Proposes Transmission Links to North Coast Offshore Wind Resources

April 3, 2024

Energy Law

In its 2023–2024 Draft Transmission Plan (Draft Plan) released on April 1, the California Independent System Operator (CAISO) proposed the development of 26 transmission projects with an estimated cost of $6.1 billion. The proposed projects are needed to connect 85 gigawatts (GW) of new electric generation that the state will need by 2035 to meet increased demand from the electrification of the transportation and building sectors and to achieve clean energy and greenhouse gas emission-reduction goals. The projects include a new 500 kilovolt (kV) Humboldt substation and two 500 kV transmission lines that will connect offshore wind resources in the North Coast area with urban load centers.

Developed in close coordination with the California Public Utilities Commission (CPUC) and the California Energy Commission, the Draft Plan continues these agencies’ efforts to better synchronize resource planning and transmission planning. The transmission projects are needed to maintain reliability and to connect 85 GW of new resources that the CPUC identified as needed by 2035 to meet load growth and achieve zero-carbon goals. The projected resource needs include 38 GW of new solar generation, 21 GW of geothermal resources, and 4.7 GW of offshore wind, split between the Morro Bay call area on the Central Coast and the Humboldt call area on the North Coast.

Offshore wind resources on the North Coast have tremendous potential, but the lack of significant transmission lines to this remote area put a damper on development. The Draft Plan proposes substantial new transmission projects to integrate North Coast offshore wind with the bulk power grid serving most of California:

  • A new 500 kV Humboldt substation
  • A new 260-mile, 500 kV High-Voltage Direct Current (HVDC) line to interconnect the new 500 kV Humboldt substation to the Collinsville 500 kV substation in the Bay Area
  • A new 140-mile, 500 kV Alternating Current line to interconnect the new Humboldt 500 kV substation to the 500 kV Fern Road substation

The CAISO will conduct a competitive solicitation to select the sponsors who will construct, own, and operate these projects. The project sponsors for the new transmission lines will face the challenge of finding routes that traverse the mountains of the Coast Range and weave through a patchwork of national and state parks, tribal lands, and wilderness areas.

As part of the 2023-2024 Transmission Planning Process, the CAISO also reviewed the Pacific Transmission Expansion (PTE) Project, an undersea HVDC cable connecting the Diablo Canyon 500 kV substation to various 230 kV substations in the Los Angeles area. The Draft Plan notes that the PTE Project has the potential to improve access to offshore wind in the Central Coast area, to reduce congestion, and to reduce gas-fired generation. The CAISO has discussed a possible joint effort with the Los Angeles Department of Water and Power, but those discussions have not yet resulted in a decision to move forward with the project.

Following stakeholder meetings on April 9 and comments due on April 23, the CAISO Board of Governors will review and adopt the Final Transmission Plan in May.