Sonoma Clean Power partners with Stem to provide smart batteries for large businesses

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Sonoma Clean Power is partnering with a provider of smart batteries to offer large commercial and industrial businesses the chance to save as much as 50 percent on their monthly energy bills.

The partnership with Millbrae-based Stem, announced Tuesday, will allow as many as 150 large business in Sonoma and Mendocino counties to install software-controlled batteries that provide power during peak demand times when electricity is most costly, account executive Nate Kinsey said.

Sonoma Clean Power, a public electricity provider serving about 220,000 customers in Sonoma and Mendocino counties, hopes at least 60 of those large companies will use the battery packs, which recharge at low-demand energy times.

The power company will conduct outreach to these businesses — considered “super users” of energy — to help them understand the potential savings. The process could take up to 13 months from initial contact to installation, Kinsey said.

Businesses pay a monthly service fee for the batteries, which are installed and owned by Stem and connected to the PG&E grid, said Sonoma Clean Power Program Manager Nelson Lomeli. Each customer can expect annual savings between $20,000 and $70,000, he said.

Stem guarantees those savings will be more than the cost of the unspecified monthly service fee, which it described as proprietary.

“This is really exciting — it’s another tool in the toolbox,” said Polly Shaw, Stem’s vice president of regulatory affairs and communications.

The systems have energy capacities ranging from 36 kilowatts an hour to 10 megawatts an hour, Lomeli said. For comparison, the lower range is the equivalent of 2,000 LED light bulbs turning on at once and shining for two hours using battery power, he said. The higher range is the equivalent of 555,556 LED light bulbs shining collectively for two hours on battery power, he said.

Companies that use the battery packs, which are the size of a gym locker, can also choose to be part of a “virtual power plant” network, allowing them to provide power to other entities in a wholesale market, Lomeli said.

The partnership, which comes at no cost to Sonoma Clean Power, is the result of a process to solicit proposals early this year, Lomeli said.

“Batteries in general have come down in price to the point that they’re accessible to businesses as a way to reduce costs,” Lomeli said. “They’re no longer limited to just helping you power your cellphone.”

Sonoma Clean Power hopes to expand energy storage to homes and other businesses, but there’s no timeline for such an arrangement, he said.

Kendall-Jackson Winery in 2015 installed Tesla batteries to help provide power in peak times. Separately, Stem in 2017 partnered with SunPower, which provided solar panels and electricity storage to Santa Rosa Junior College.

You can reach Staff Writer Hannah Beausang at 707-521-5214 or On Twitter @hannahbeausang.

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