The recent test event in California showcased the power of over 100,000 home batteries acting as a virtual power plant. The analysis conducted by The Brattle Group revealed that Sunrun emerged as the largest aggregator, with Tesla leading as the largest OEM. Most of the batteries were enrolled in California’s Demand-Side Grid Support (DSGS) program.
During the two-hour grid support test on July 29, Sunrun’s distributed battery fleet contributed over two-thirds of the energy, totaling an average of 535 megawatts (MW) pumped onto the grid. This amount of energy was sufficient to power over half of San Francisco. The event, which took place between 7 and 9 pm, was a collaborative effort by the California Energy Commission, CAISO, and utilities to prepare for grid stress during upcoming heat waves in August and September.
Sunrun’s batteries played a crucial role by delivering an average of over 360 MW during the test event, aligning perfectly with the peak electricity demand in the evening. The consistent performance without any major fluctuations or attrition impressed Ryan Hledik, a principal at The Brattle Group, who described it as “dependable, planning-grade performance at scale.”
The analysis highlighted the significant impact of residential batteries in reducing statewide grid load during peak demand hours. Hledik emphasized that these batteries not only help shave off demand but also reduce the necessity for new power plants. Sunrun’s fleet had already demonstrated its capabilities by delivering 325 MW during a similar event on June 24, with customers being compensated up to $150 per battery per season for participating.
Sunrun CEO Mary Powell emphasized the importance of distributed home batteries as a powerful and flexible resource that can prevent blackouts, alleviate peak demand, and reduce extreme price spikes. The success of these events underscores the potential of residential batteries in supporting grid stability and reliability.
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