California Energy Storage Showcase

Battery energy storage systems are being used to accomplish a variety of the functionalities of grid-scale battery energy storage.

Pacific Gas & Electric (PG&E) has installed two sodium sulfur battery energy storage systems (BESSs) to evaluate the system performance in supplying a variety of power grid functions. The first system was installed at the PG&E Vaca-Dixon substation. The objective is to analyze various energy storage use scenarios and gain knowledge on how future systems can be implemented within the power grid. The second system installation is at the Hitachi Global Storage technologies facility in San Jose. Here, the objective is to mitigate fluctuations and enhance power reliability for customers on the distribution line. The large capacity of the battery will allow the Hitachi facility to be fully powered by the battery in the event of an outage.

See more information about Molten Sulfur Energy Storage Used for Backup Power.

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Demonstrating the value of energy storage to provide:

  • Reliability
  • Renewable integration
  • Ancillary services

Type of Technology

Sodium-sulfur battery – A molten salt battery that has relatively high energy density, good efficiency, and a long cycle life, but generally must be operated at high temperatures and with additional protections for corrosion.

Quick Facts

  • Power Capacity Ratings: 2 MW at PG&E's Vaca-Dixon substation; 4 MW in San Jose, California
  • Energy Capacity Ratings: 14 MWh at Vaca-Dixon; 28 MWh in San Jose, California
  • Type of Energy Storage: Sodium-Sulfur batteries (NaS)

Key Developers and Partners

  • PG&E
  • NGK Insulators (Sodium Sulfur battery systems)
  • S&C Electric Company (Power Conversion Equipment and EPC Contractor)

Energy Commission Funding



Deployed and used for testing and demonstration purposes.


Location of Molten Sulfur Energy Storage Used for Backup Power in California