Rocky Mountain Power is expanding its efforts to support residential solar users in Utah by targeting homeowners without backup battery systems. Following the success of its virtual power plant (VPP) program, the utility has partnered with sonnen, a VPP provider, and ES Solar, a solar installation company, to introduce the Go Back initiative, a new model for its Wattsmart VPP program.
Successful Retrofits and Growing Demand
Through the Go Back program, ES Solar has successfully sold 18 MWh of its retrofit energy storage systems. The company installs between 200 to 500 batteries monthly across Utah, with Rocky Mountain Power customers making up over 75% of these sales this year. The utility benefits from this arrangement by utilizing customers’ battery storage to manage peak electricity loads, making these distributed energy resources (DER) crucial for balancing the fluctuations associated with intermittent solar energy.
Understanding the Wattsmart Virtual Power Plant
Since its launch in December 2020, the Wattsmart program has expanded to encompass over 40 MWh of capacity, attracting thousands of participants. The program incentivizes solar owners to connect grid-compatible batteries, offering an upfront payment of $600 per kW for those interested in adding a battery to their solar system. New solar and battery installations after 2021 can qualify for $400 per kW. ES Solar reports a remarkable 95% attachment rate for batteries among its new solar customers, with over 90% of them choosing to enroll in the Wattsmart VPP.
The program aggregates the energy stored in all participating batteries, creating a significant resource that can provide energy during peak demand periods, such as heatwaves or emergencies. By utilizing excess solar energy to charge these batteries during the day, Rocky Mountain Power can draw upon this stored energy when demand peaks after sunset.
The Role of Sonnen’s VPP Software
Sonnen’s advanced VPP software connects local residential and commercial DER networks into a unified system, allowing for the on-demand deployment of stored energy. Sonnen entered the VPP landscape in 2018, collaborating with Rocky Mountain Power and a local developer to create Soleil Lofts, an all-electric apartment complex centered around a grid-connected VPP. This project served as a foundational model for Rocky Mountain Power’s subsequent DER initiatives.
Currently, Rocky Mountain Power has approximately 80,000 solar customers without smart grid-interactive batteries. Over the next five years, ES Solar aims to retrofit 40% of Utah’s residential solar systems with sonnen’s VPP batteries, covering about 32,000 homes.
The Value of Virtual Power Plants
Rocky Mountain Power claims to be the only vertically integrated utility in the nation with a behind-the-meter battery VPP that operates without relying on external DER management software. Instead, the utility utilizes its own battery grid management system, which facilitates direct control of batteries for grid operations and eliminates common integration issues associated with standalone solar installations.
According to the U.S. Department of Energy, the popularity of VPPs is on the rise, with current deployments estimated at 30 to 60 GW across the nation. These programs are poised to address an expected 60 GW increase in coincident peak demand on the U.S. power grid by 2030. By tripling the number of existing VPPs, they could potentially meet 10-20% of this demand.
PacifiCorp, the parent company of Rocky Mountain Power, reports that it has achieved a capacity savings of 1.1 GW through demand response initiatives. The company also operates Pacific Power, serving regions of Oregon, California, and Washington.
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