Several communities in King County have temporarily banned the siting of large-scale battery systems. But the Snohomish County Public Utility District is getting ready to power up Washington’s first — and so far, largest — such system this fall.

The utility district told KNKX it selected the best technology available and was able to build it on the district’s “clean energy campus” in Arlington. The City of Arlington has a policy in place to support the permitting process and stave off objections that have been growing in other communities.

The Tesla-made batteries are locked up inside rows and rows of vented white lockers on a gravel lot. They are designed to store excess power from sources like wind and solar, which are clean but don’t always generate power when needed. And the batteries are needed as the state’s zero-emissions mandates kick in.

Gabriel Duran is supervising the construction for design firm Ameresco. An electrical engineer who specializes in solar systems, he said this is his fifth battery energy storage project and his first in Washington.

“I wasn’t involved in the selection of this particular technology, but as I’ve learned about it, I think it’s fantastic,” he said. “Especially the computer system managing it, and all the data that we can both interpret and respond to, is pretty cutting edge.”

The system is designed to add capacity to the grid — enough electricity to run tens of thousands of homes for a few hours. And it will help the utility keep power affordable, because it won’t have to buy as much on the open market, said program manager Jessica Spahr.

“When we have those significant weather events — either a cold snap or a heat wave — and we have to purchase that really high peak‑demand power, this will help smooth that out a little bit more and keep those costs low,” Spahr said.

Additionally, Spahr said the system includes state-of-the-art fire suppression and detection.

“We feel it’s the safest type of technology that we could provide for this type of system, and the need and the benefits we feel are balanced with the risks that have been identified,” she said.

The Arlington project likely won’t be the state’s largest battery system for long. Another one currently under construction in the Pierce County city of Sumner will be about eight times as large.

Other places have seen controversy surrounding such projects.

Last year, a battery storage fire burned for days in Moss Landing, California, triggering evacuation orders for more than 1,000 people. That scenario has been cited frequently by opponents of a proposed battery storage facility in Snoqualmie.

Snoqualmie is one of at least eight communities in King County that have temporarily banned the siting of battery energy storage systems.

Bellamy Pailthorp is a reporter with KNKX. This story comes to you from the Northwest News Network, a collaboration between public media organizations in Oregon and Washington.

It is part of OPB’s broader effort to ensure that everyone in our region has access to quality journalism that informs, entertains and enriches their lives. To learn more, visit our journalism partnerships page.

News Source : https://www.opb.org/article/2026/08/03/snohomish-county-building-largest-battery-plant-in-washington/