PG&E Fires Up New BESS in Moss

Written by Neil Farrell

Neil has been a journalist covering the Estero Bay Area for over 27 years. He’s won numerous journalism awards in several different categories over his career.

June 3, 2022

Pacific Gas & Electric Co., has completed another giant battery plant and, after successful testing, was powered up and slated to go online in April.

Named the “Elkhorn Battery” the 182.5-megawatt facility is located on the property of the Moss Landing Power Plant. It uses Tesla’s Megapack technology of lithium ion batteries, according to a news release from PG&E. 

Elkhorn was fully energized and the California Independent System Operator or Cal-ISO, the State agency that operates the power grid, was expecting to put it into service by April 7.

“We are ushering in a new era of electric system reliability,” PG&E’s Corporation Chief Executive Officer Patti Poppe said in a news release, “and delivering a vision into the future for our customers with the commissioning of the Tesla Megapack system in Moss Landing. 

“We are committed to safely delivering reliable and clean energy in a way that achieves the greatest value for our customers, but we can’t go it alone into this clean energy future. Projects like this require innovative partners, such as Tesla, and PG&E will continue to seek out and work with the best and brightest to provide breakthrough clean energy solutions for our customers.”

Battery energy storage, the company said, helps integrate renewable energy sources, like solar, and also enhances the overall reliability of California’s ever-changing energy supply. Batteries are charged when energy demand is low or when solar production is high, and then provide additional capacity by sending that reserved power to the grid when demand grows.

The Elkhorn project seems to have gotten a green light for fast-tracking, which might be a hint at how much the State of California wants to push sustainable, carbon-free, non-fossil fuel energy sources, a huge component of which is energy storage facilities like PG&E’s Elkhorn plant.

The Elkhorn BESS “was approved by the California Public Utilities Commission in November 2018 and by the Monterey County Planning commission in February 2020, the news release said. “Site construction began in July 2020.”

The Elkhorn Battery system is named for the Elkhorn Slough in Moss Landing, a major estuary of Monterey Bay. It was designed, constructed, and is maintained by both PG&E and Tesla, but owned and operated by PG&E, the company said.

The facility boasts 256 Tesla Megapack battery units on 33 concrete slabs. Each unit houses batteries and power conversion equipment in a single cabinet. Transformers and switchgears were also installed along to connect energy stored in the batteries with 115-kilovolt transmission wires.

The BESS has the capacity to store and dispatch up to 730-megawatt hours of energy to the power grid at a maximum rate of 182.5 MW for up to 4 hours during periods of high demand.

It’s a key piece to the State’s transforming energy puzzle. “The Elkhorn Battery,” PG&E said, “enhances reliability by addressing capacity deficiencies that have resulted from increased local energy demand. It participates in the CAISO wholesale electric markets, providing energy and ancillary service such as serving as an operating reserve that can quickly be dispatched to ensure there is sufficient energy to meet demand to the CAISO-controlled grid.”

The new facility is one of the largest lithium-ion battery storage facilities in the world. Currently, the largest in the world is a 300 MW BESS owned by Vistra Energy and also located at Moss Landing. It’s one of two the Texas-based energy company has at Moss, including a 100 MW BESS. Vistra also owns the Moss Landing plant and property, which was originally built by PG&E in the 1960s and sold to Duke Energy, along with three others plants including Morro Bay, in 1998 during California’s flirtation with deregulation of the energy industry.

Vistra also filed in January to build another BESS at Moss Landing, a 350-MW facility that will bring the company’s total storage capacity at the site to 750 MW, according to a January article on, an online industry publication.

It would be the third phase of the company’s plans for the old power plant, which was a sister plant to the closed Morro Bay Power Plant. Duke Energy was able to build a combined cycle, natural gas fueled, 1,200 MW power plant at Moss Landing in the early 2000s, even as it failed to get permits to build the exact same type and make and model of plant to replace the Morro Bay plant, which dates back to the late 1950s and early ‘60s. Vistra closed the Morro Bay plant in 2014.

Vistra has said it plans to grow its zero-carbon ‘Vistra Zero’ portfolio to 7,300 MW by 2026, the article reported. “That total includes 5,000 MW of renewables and energy storage, along with the company’s 2,300-MW Comanche Peak nuclear power plant in Glen Rose, Texas.

“Vistra currently has six solar power installations and 11 other energy storage and solar-plus-storage projects in various stages of development and operation in Texas and Illinois, in addition to its California holdings.”

Those pending projects include a 600 MW BESS proposed for a 22-acre site on the Morro Bay Power Plant property. That project is still being evaluated by the Morro Bay Planning Department and has yet to go to the planning commission for what’s anticipated to be the first of several hearings on the project.

PG&E’s new BESS in Moss Landing is one of several the utility company has under contract in its efforts to green up its energy portfolio. 

“PG&E,” the company said, “now has contracts for battery energy storage systems totaling more than 3,330 MW of capacity being deployed throughout California through 2024.

“To date, 955.5 MW of new battery storage capacity has been connected to California’s electric grid including:

• 182.5 MW PG&E Elkhorn Battery in Monterey County (commissioned 2022);

• 200 MW Diablo Storage System in Contra Costa County (2022);

• 60 MW Coso Battery Storage in Inyo County (2022);

• 400 MW Vistra Moss Landing Battery Energy Storage Facility (2021);

• 63 MW NextEra Blythe system in Riverside County (2021); and,

• 50 MW Gateway system in San Diego County (2021).”

PG&E predicts that another 1,400-plus MW of storage capacity out of the 3,330 MW under contract will come online in 2022 and 2023, the company said.

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