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German home energy storage and virtual power plant (VPP) company sonnen and solar contractor ES Solar are expanding a Utah and Idaho VPP programme to include up to 35MWh of residential batteries by the end of the year.

The Wattsmart programme from utility Rocky Mountain Power (RMP) was approved by the Idaho Public Utilities Commission in April this year. The programme gives home battery owners the option to give RMP some control of the battery system to support the grid, in exchange for an upfront incentive and ongoing bill credits.

RMP has direct control over the batteries enrolled and can dispatch it on demand to meet grid conditions with daily solar time shifting and load curtailment, as well as frequency response services and directed solar grid injection when the grid needs power the most.

ES Solar expects to bring up to 35MWh of grid-interactive battery capacity online in 2022 via the Wattsmart programme. The company said that sonnen energy storage sales are reaching over 6MWh a month, thanks to the programme.

RMP has in recent years ended its solar net metering subsidy scheme to shift focus towards a model of home solar-plus-storage with the Wattsmart programme. The model, it claimed, is helping build the largest network of utility dispatched smart residential batteries in the US. ES Solar was the first contractor in Utah to deploy the model.

ES Solar said it has a 98% smart, utility-controlled battery attachment rate on new solar PV sales as part of the Wattsmart programme, with over 2,000 batteries enrolled already. It is on track to reach an estimated 1,500 additional customers by the end of 2022 and more than 5,000 in 2023. It is mainly targeting existing solar owners to retrofit batteries.

ES Solar team is the first contractor to have access to sonnen’s newest technology, the stackable sonnenCore+ System, which ES launched in July 2022.

Blake Richetta, Chairman and CEO at sonnen, commented: “As Rocky Mountain Power’s battery programme grows, ES Solar is succeeding in overcoming the complex concepts and challenges associated with effectively integrating residential solar-plus-storage into the broader energy system.”

“As this radical model expands into thousands of new homes, so does the use of batteries for the betterment of individuals, society and the environment, which is the ultimate purpose of a solar battery.”

The programme is one of several high-profile VPP projects to be making headways in the US market.

Last week, California utility PG&E’s CEO tweeted a significant update about a VPP programme it launched with Tesla in July, covered by Energy-Storage.news. Patti Poppe said that nearly 2,500 PG&E customers delivered up to 16.5MW of solar power to the grid as the system was activated.