Washington’s Largest Battery Storage To Power Up in Arlington in Fall 2026 — Despite Local Bans

Washington State’s Snohomish County Public Utility District (PUD) is preparing to commission a large-scale battery energy storage system in Arlington in fall 2026, even as several neighboring communities in King County have paused similar projects. The installation, described by local media as the state’s first and largest, is part of the utility’s clean energy campus and is designed to store renewable electricity and deliver it when demand — and prices — spike.

The batteries, supplied in vented white enclosures manufactured by Tesla, sit across a gravel lot and are managed by an advanced control and data system. Gabriel Duran, who is supervising construction for design firm Ameresco, said the sophistication of the computer controls and the real-time data monitoring are among the project’s most notable features.

“Especially the computer system managing it, and all the data that we can both interpret and respond to, is pretty cutting edge,” Duran said.

At least eight King County jurisdictions, including the city of Snoqualmie, have adopted temporary moratoria on siting battery energy storage systems amid public safety concerns. By contrast, Arlington has adopted permitting policies designed to facilitate siting of energy storage projects, which allowed the PUD to move forward at its clean energy campus without local delay.

Snohomish County PUD expects the Arlington facility to provide enough capacity to power many thousands of homes for several hours during peak demand. A much larger installation under construction in Sumner is expected to be roughly eight times the size of the Arlington project, meaning the state-size record may be short-lived.

Why Utilities Want Large Batteries

Large battery systems let utilities capture electricity produced by wind and solar and discharge it later when demand and prices are highest. That capability is especially valuable during extreme weather — heat waves or cold snaps — when demand surges and power purchased on the open market can become very expensive. Program manager Jessica Spahr said the storage system will help smooth demand spikes and keep costs low for customers.

“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.

Safety Concerns And Mitigations

Safety worries have mounted in some communities after a multi-day fire at a battery storage facility in Moss Landing, California, which led to evacuations affecting more than 1,000 people. Opponents cite that incident when urging caution or pauses on new projects.

To address those concerns, Snohomish County PUD says it selected the clean energy campus site and a system design with a strong safety profile. The Arlington installation includes advanced fire-detection and fire-suppression systems, redundant monitoring, and other risk-mitigation features intended to reduce the likelihood and impact of any incident.

As more large-scale battery projects move forward across Washington, utilities say successful deployments could increase the amount of low-cost renewable energy they can store, reduce expensive peak market purchases, and improve the resilience and affordability of electric service during periods of high demand.