ES Solar and sonnen find US success with Wattsmart VPP program in Utah

US utility Rocky Mountain Power’s (RMP) Wattsmart Battery Program, a model for selling grid-interactive solar and utility-controlled residential batteries, is an alternative to solar “grid defection” and eliminates reliance on net metering.

Under the program, Utah ratepayers with solar installations can upgrade their system to include a grid-interactive smart sonnen battery designed to harness solar and harmonize it with greater grid operation. The utility, RMP, offers Go Back incentives for a Wattsmart Battery, an annual bill credit for grid services, and proactive backup power.

Utah-based installer ESS reports it has sold 18 MWh of retrofitted sonnen energy storage systems under the Go Back initiative part of the greater Wattsmart Program in Utah. ESS estimates that more than 75% of its 2024 sales have been through the Go Back Program, resulting in between 200 and 500 sonnen battery installations in Utah each month.

ESS reports that RMP has directly integrated its specialized customer-side, “behind-the-meter” battery VPP into its grid operating system without a distributed energy resources management system solution in the middle. The utility does this while dispatching the battery fleet every day, deploying up to eight genuine grid services that are focused on electrochemical energy storage technology.

The RMP Wattsmart Distributed Battery Grid Management System VPP has grown to more than 40 MWh of energy capacity, a substantial portion of which was sold by ESS. RMP customers who installed solar before September 1, 2021 may qualify for an upfront incentive of $600/kW on their battery system by enrolling in Wattsmart, according to ESS. 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, vice president of sales at ESS.

In addition to their Go Back business, ESS reports experiencing a 95% battery attachment rate for new solar sales, with more than 90% of those customers enrolling in the Wattsmart VPP. Following installation, those batteries are dispatched daily to carefully sculpt and flex PV generation and load.

From pv magazine USA.