As California heads into another summer of high electricity demand, a growing network of residential batteries is poised to play a larger role in maintaining grid reliability. Sunrun’s CalReady program—part of the state’s Demand Side Grid Support initiative—has expanded significantly, now aggregating power from more than 56,000 homes equipped with solar-plus-storage systems.
According to data released this week, CalReady will tap into roughly 75,000 batteries this season to deliver flexible energy support to the grid between 4 and 9 p.m., the peak hours of demand from May through October. This marks the second year the program has been operational, and it has quickly grown into the largest virtual power plant (VPP) in California, and among the largest in the country.
The virtual plant’s expected output has jumped from 48 megawatts on average last summer to around 250 megawatts per event in 2025, with the potential to peak at 375 megawatts—enough to power the equivalent of 280,000 homes.
Unlike traditional utility-scale storage, CalReady relies entirely on distributed residential systems. This decentralized model offers operational flexibility and increased grid resilience, without the need for new land use or major infrastructure investments.
“This level of scale is a testament to how distributed energy resources (DERs) can serve as a critical complement to centralized grid assets,” said Paul Dickson, president and chief revenue officer at Sunrun. “We're demonstrating that coordinated, customer-sited resources can provide real capacity when and where it’s needed most.”
CalReady is designed to activate during high-price or high-stress periods for the grid. In return, participating customers receive financial compensation for the energy their systems contribute—up to $150 per battery. Last year, participants earned a combined $1.5 million. This year, Sunrun estimates it will distribute nearly $10 million to enrolled households.
For utilities and system operators, CalReady provides an increasingly important tool for demand flexibility, particularly as electrification and extreme weather strain California’s aging grid. In addition to reducing emissions and wholesale power costs, distributed programs like CalReady can also help defer or avoid expensive infrastructure upgrades.
From a customer perspective, the program offers a chance to monetize home storage assets while preserving outage protection. Batteries enrolled in CalReady retain at least a 20% reserve for backup use during local outages.
The growth of the program mirrors broader adoption trends: by the end of 2024, more than 60% of new Sunrun customers nationwide added battery storage to their solar systems. In California, that number was closer to 90%.
