Worlds Largest Lithium BESS completed in California

Vistra Energy has declared the successful completion of the expansion work at its Moss Landing Energy Storage Facility in California, which stands as the world’s largest lithium battery energy storage system (BESS) asset.

Vistra, a company engaged in power generation and retail, recently revealed that the Phase III expansion commenced commercial operations at the beginning of June.

This expansion has brought an additional 350MW output and 1,400MWh energy capacity to the plant, resulting in a combined total of 750MW/3,000MWh.

This follows the completion of Phase I, a 300MW/1,200MWh segment, in 2020, followed by the incorporation of another 100MW/400MWh in Phase II the subsequent year.

Just as in the previous two phases, the offtaker for the new battery units will be Pacific Gas & Electric (PG&E), a California investor-owned utility (IOU). PG&E has contracted with Vistra to ensure resource adequacy (RA), a mechanism in California that guarantees the dependable delivery of energy to customers by electric load-serving entities.

RA is the principal factor driving California’s leadership in grid-scale BESS deployments. The prospect of securing long-term contracts with associated revenue streams from electricity suppliers has propelled the market to exceed 5GW within the main CAISO grid service region.

RA mandates involve delivering electricity in four-hour increments, which is why most new battery storage facilities in the state have durations of that length.


PG&E’s newly inked contract for Moss Landing Phase III, referred to as MOSS350, spans a 15-year term and gained regulatory approval from California authorities in April 2022.

Vistra Energy highlighted that the expansion was executed within the planned 16-month period, incorporating over 110,000 battery modules within 112 containerized units. The project remained on track, as announced in Vistra’s recent financial results in May.

Leveraging the infrastructure of an existing Vistra natural gas power plant on the same site facilitated the project’s development. This location factor eliminated zoning challenges and permits the potential for further expansion of the BESS facility, according to Jim Burke, CEO and president of Vistra Energy.

Vistra has previously suggested that the Moss Landing Energy Storage Facility could eventually accommodate 1.5GW/6GWh of battery storage, contingent on favorable market conditions. PG&E, in the same Moss Landing site, owns the Elkhorn Battery project, a BESS plant with a capacity of 182.5MW/730MWh.

Jim Burke remarked, “As we navigate this energy transition to cleaner fuel sources, the ability to balance that shift with both reliability and affordability is paramount. Continued investment in energy storage, like our Moss Landing site, allows us to harness and store a substantial and growing amount of power from intermittent renewables and then deliver that electricity when customers need it most.”

Despite experiencing operational challenges in its initial years, particularly overheating incidents, the Moss Landing Energy Storage Facility continues to hold the distinction of being the world’s largest BESS project, further fortified by this recent expansion.

While other notably large projects are in the development pipeline, such as Australia’s Waratah Super Battery and the UK’s Carlton Power project, both surpassing gigawatt-hour capacity, Vistra’s ambitious plans to achieve over 1.2GW of battery storage in its US portfolio by 2026 remain noteworthy. Vistra’s diversified assets span renewables, fossil fuels, nuclear, and energy storage.