Battery maker sonnen and contractor ES Solar today announced initial results of their “Go Back” program, a new VPP business model enabled by Rocky Mountain Power (RMP), targeting existing residential solar customers.
The program allows Utah homeowners with existing solar installations to upgrade their systems to include a grid-interactive sonnen battery. Customers gain access to a higher upfront Wattsmart Battery incentive from RMP, an annual bill credit for grid services and proactive backup power.
ES Solar has already sold 18 MWh of sonnen retrofit energy storage systems via the Go Back initiative within the greater Wattsmart Program in Utah. The company estimates that more than 75% of its 2024 sales are via the Go Back Program, resulting in upwards of 500 sonnen battery installations in Utah each month.
RMP, a pioneer among utilities in the VPP field, enables ES Solar and other solar contractors interested in selling the Wattsmart Go Back program with the opportunity to sell an upfront incentive due to the enhanced value that “firming” existing solar has to the energy system. This approach demonstrates a sharp contrast to the standard “new solar new battery” Wattsmart business model.
RMP is likely the only U.S. utility that has directly integrated its own behind-the-meter battery VPP into its grid operating system without a distributed energy resources management system (DERMS) solution in the middle. RMP’s Wattsmart VPP is a fully scalable program that is service-territory-wide. The RMP Wattsmart Distributed Battery Grid Management System (DBGMS) VPP has now grown to over 40 MWh of energy capacity, a substantial portion of which was sold by ES Solar.
RMP customers who have installed solar prior to Sept. 1, 2021, may qualify for an upfront incentive of $600/kW on their battery system by enrolling in Wattsmart. Comparatively, Wattsmart customers installing both new solar and a new battery may qualify for $400/kW.
“Existing solar customers are very interested in adding an intelligent energy storage system to their solar array, not just for backup power, but for the other benefits that a storage system can provide,” said Zach Randall, VP of Sales at ES Solar. “The battery Go Back business model is also an excellent method to smooth out a solar contractor’s business over the course of the year, by providing a terrific opportunity for high-volume during the winter months.”
In addition to its Go Back business, ES Solar has reported a 95% battery attachment rate for new solar sales, with over 90% of these customers enrolling in the Wattsmart VPP.
“ES Solar’s work in the RMP service area to date is an ideal case study which illustrates the potential national impact and scalability of a grid harmonizing, as opposed to grid defecting business model,” said Blake Richetta, Chairman and CEO of sonnen USA. “Using batteries to firm existing solar and enable the implementation of flexible DER systems and VPPs is the key to supporting genuine energy transition for humanity.”
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