California's Groundbreaking Virtual Power Plant Test
In a remarkable demonstration of the potential of distributed energy resources, over 100,000 residential batteries across California were simultaneously activated on July 29, delivering an impressive average of 535 MW of power during the critical hours of 7 to 9 p.m. This statewide test, analyzed by the consultancy Brattle, showcased the ability of these batteries to support the grid during challenging times, particularly when solar generation wanes in the evening.
The test, conducted in preparation for anticipated demand during the upcoming August and September heat waves, was coordinated by virtual power plant (VPP) aggregators Sunrun and Tesla. Sunrun, responsible for aggregating two-thirds of the participating batteries, emphasized the daily capability of these resources to provide essential energy support. Participating battery owners were compensated by Sunrun, while the aggregator itself received payment for dispatching the batteries.
Battery operations before and during the test event.
Image: The Brattle Group
Brattle's analysis highlighted the potential of VPPs to reduce the need for new generating capacity and alleviate strain on the system during the evening load ramp, commonly referred to as the duck curve. The test day results, as shown in the image provided by Brattle, demonstrate a significant reduction in CAISO's system net load, which represents total electricity consumption minus distributed generation.
The vast majority of the participating batteries, nearly 90%, were enrolled in California's Demand-Side Grid Support program. This program incentivizes customers to reduce load or provide backup generation during extreme events from May to October, thereby mitigating the risk of rotating power outages.
Image: The Brattle Group
Brattle commended the consistent output of the batteries during the test, noting the absence of significant fluctuations or performance attrition. Sunrun CEO Mary Powell hailed the customer-led solution as a win-win for households and the grid, emphasizing the power and flexibility of distributed home batteries in delivering reliable power, preventing blackouts, alleviating peak demand, and reducing extreme price spikes.
Looking ahead, Brattle anticipates the scale of VPP capacity in California from residential batteries to grow substantially. The consultancy believes that events like this VPP test will help convince system operators of the dependable, planning-grade performance that VPPs can provide at scale.
The successful coordination among aggregators, the California Energy Commission, CAISO, and the state's three major utilities during the test underscores the collaborative effort required to harness the full potential of residential batteries as a distributed energy resource.
As the energy landscape continues to evolve, this groundbreaking test in California serves as a compelling example of how VPPs can pave the way for a more resilient, sustainable, and cost-effective energy future.
