California Successfully Tests 'Virtual Power Plant', Drawing Power From Batteries in 100,000 Homes

'California's biggest electric utilities pulled off a record-breaking test...' reports Semafor, 'during the 7pm-9pm window that is typically its time of peak demand as people come home from work.'

Pacific Gas & Electric and other top California power companies switched on residential batteries in more than 100,000 homes and drew power from them into the broader statewide grid. The purpose of the test — the largest ever in the state, which has by far the most home battery capacity in the U.S. — was to see just how much power is really there for the utility to tap, and to ensure it could be switched on, effectively running the grid in reverse, without causing a crash.

The result, which the research firm Brattle published this week, was 535 megawatts, equal to adding a big hydro dam or a half-sized nuclear reactor at a fraction of the cost. 'Four years ago this capacity didn't even exist,' Kendrick Li, PG&E's director of clean energy programs, told Semafor. 'Now it's a really attractive option for us. It would be silly not to harness what our customers have installed....' Last week's test proved that in times of peak demand, PG&E can lean on its customers' batteries rather than turn on a gas-fired peaker plant or risk a blackout, Li said.

Virtual power plants (VPPs) also facilitate the addition of more solar energy on the grid: At the moment, California has so much solar generation at peak hours that it can push the wholesale power price close to or even below zero, a headache for grid managers and a disincentive for renewable project developers. The careful manipulation of networked residential batteries smooths out the timing disparity between peak sunshine at midday and peak demand in the evening, allowing the excess to be soaked up and redeployed when it's actually needed, and making power cheaper for everyone. The expanded use of VPPs shouldn't be noticeable to battery owners, Li said, except for the money back on their power bill; nothing about the process prevents them from running their AC or dishwasher while their battery is being tapped. The network can also run in reverse, with the utility taking excess power from the grid at times of low demand and sending it into home batteries for storage.

California could easily reach over a gigawatt of VPP capacity within five years, Li said. Nationwide, a Department of Energy study during the Biden administration forecast that VPP capacity could reach up to 160 gigawatts by 2030, essentially negating the need for dozens of new fossil fuel power plants, with no emissions and at a far lower cost. In 2024, utilities in 34 states moved to initiate or expand VPP networks, according to the advocacy group VP3.

Even with a reduction in federal credits, virtual power plants 'offer a way for residential solar-plus-storage systems to remain economically attractive for homeowners — who get paid for the withdrawn power,' the article points out — and 'a way to make better use of clean energy resources that have already been built.'

Sunrun's distributed battery fleet 'delivered more than two-thirds of the energy,' notes Electrek, 'In total, the event pumped an average of 535 megawatts (MW) onto the grid — enough to power over half of San Francisco... This isn't a one-off. Sunrun's fleet already helped drop peak demand earlier this summer, delivering 325 MW during a similar event on June 24.

'The company compensates customers up to $150 per battery per season for participating.'

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