Ameresco to build 50MW/200MWh BESS in California

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System integrator Ameresco will build a maximum 50MW/200MWh battery energy storage system (BESS) in partnership with Silicon Valley Power (SVP), the non-profit utility of the city of Santa Clara, California.

Ameresco will build, own and operate the BESS – on which construction is due to begin in mid-2024 – whilst charging power will be supplied by SVP from its excess renewable energy generation. The project is expected to be operational by Q4 2025.

“This 50-megawatt battery energy storage system represents a significant step towards enhancing Silicon Valley Power’s system reliability,” said Jovan Grogan, Santa Clara City manager and Silicon Valley Power CEO. “Together with Ameresco, we are paving the way for a more resilient and sustainable energy future for our city.”

The BESS will participate in the California Independent System Operator (CAISO) markets, aiding in grid stability and balancing consumption. This is a particularly pertinent issue for CAISO following the report earlier this month which found that the system operator had been curtailing its solar PV generation more in the last year than at any other time, largely due to transmission capacity congestion. CAISO has said that developing flexible resources like energy storage systems will be key to lessening grid congestion.

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Earlier this year, Ameresco announced the deployment of four BESS co-located with natural gas plants across California, totalling 379MWh. Owned by independent power producer (IPP) Middle River Power, the gas plants will increase their efficiency via the addition of energy storage, opening up more capacity for the CAISO grid.

Those four projects appear to be the beneficiary of a US$250 million financing package which First Citizens Bank announced last week (16 November). The bank said the financing would go towards a portfolio of 327M/327MWh BESS projects being developed in California by Middle River Power co-located with gas plants, though it didn’t mention the technology provider.

The discrepancy in size reported may be due to one figure being nameplate and the other being the actual size deployed, because of the need to overbuild the system for DC-AC energy losses as well as accounting for long-term degradation of capacity in the battery cells. Energy-Storage.news has asked Ameresco to confirm this and will update this article in due course.

See all coverage of the company’s activity in energy storage here.

11 November 2025
San Diego, USA
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