What kind of onshore transmission would be necessary to accompany Humboldt offshore wind?

Offshore wind turbines produce a tremendous amount of electricity — far more than is needed locally here in Humboldt County. Humboldt County has also historically been under invested with transmission infrastructure. Read this report (6) by Arne Jacobsen to learn more about Humboldt's current electric infrastructure. Because our existing transmission infrastructure is extremely limited and insufficient to transmit so much energy to other parts of California, successful implementation of offshore wind would necessitate the construction of new, larger transmission lines to connect Humboldt with the rest of the State.

Reference Jacobsen (2025) (6)

The California Independent Systems Operator (CAISO) annually recommends the construction of new transmission infrastructure in a document known as the Transmission Plan. The Draft Transmission Plan for 2023-2024 (1) contains several recommendations for new transmission infrastructure specifically to serve offshore wind electricity generation, which are as follows:

• A new Humboldt 500-kilovolt AC substation

• A new 500/115-kilovolt transformer and approximately 6-mile line connecting offshore wind energy to the local Humboldt Bay grid

• A new 500-kilovolt AC line that would run approximately 140 miles east toward Redding

• A new 500-kilovolt HVDC line that would initially be operated as a 500-kilovolt AC line and run approximately 260 miles southeast toward the San Francisco Bay Area

According to CASIO, the new transmission line will likely follow the existing southern route shown in purple on the map below.

CASIO Transmission Routes from Humboldt Bay. Source: Humboldt County General Plan 2025 (5).

Click here to watch this September 2024 video from the Humboldt Bay Symposium on Offshore Wind Transmission and Climate Goals (2).

​​​The U.S. Department of Energy (DOE) and the Bureau of Ocean Energy Management (BOEM) are working together on a plan to harness wind energy from the ocean off the West Coast (California, Oregon, and Washington) and deliver it to nearby communities as reliable electricity. You can view the various development options they are considering on the DOE website (3). ​

CAISO estimates that these improvements would cost approximately $4.2 billion and would be completed by 2035. The CAISO board approved this plan on May 23rd, 2024. For more info, watch this Schatz Energy Research Center video about Offshore Wind and Transmission Infrastructure in Northwestern California (4):

​References​

1. California Independent Systems Operator. (2024, April 1). Draft 2023-2024 Transmission Plan. https://stakeholdercenter.caiso.com/InitiativeDocuments/DRAFT_2023-2024_TransmissionPlan.pdf 

2. Schatz Energy Research Center. (2024, May 29). Offshore Wind and Transmission Infrastructure in Northwestern California [Video]. YouTube. www.youtube.com/watch?v=HeWSdGb_SNY

3. U.S. Department of Energy. (n.d.). West Coast offshore wind transmission planning. Grid Deployment Office. https://www.energy.gov/gdo/west-coast-offshore-wind-transmission-planning

4. Access Humboldt. (2024a, September 12). YouTube. https://www.youtube.com/watch?v=TySArfMCglM

5. Schatz Energy Research Center, Humboldt State University. (2005, August). Humboldt County General Plan 2025 Energy Element Background Technical Report. https://humboldtgov.org/DocumentCenter/View/63211/Humboldt-County-General-Plan-Energy-Element-Background-Technical-Report-2005-PDF

6. Jacobson, A. (2025, September). Power behind the Redwood Curtain: A history of electric transmission and natural gas infrastructure in Humboldt County. Cal Poly Humboldt, Schatz Energy Research Center. https://schatzcenter.org/pubs/2025-Humboldt-Energy-Infrastructure-History.pdf