Sumner officials and Puget Sound Energy (PSE) representatives used a Jan. 13 study session to outline how battery energy storage systems — from residential “power walls” to midsize commercial arrays and utility-scale projects — may appear in the city and what safety and land-use steps the city will take next.

The presentation, led by Ryan Windisch, Sumner’s community and economic development director, and Christine Nahn of PSE, described the utility’s plan to add storage to integrate more renewable generation and meet Washington state clean-energy requirements. “Battery energy storage systems are an important part of PSE’s plan to provide reliable power our customers expect, while delivering more of the clean energy required by Washington’s clean energy requirements,” Nahn said.

Why it matters: PSE and others are planning a mix of utility-scale, midscale commercial and residential storage to help replace retiring generation and support a higher share of renewables. City staff said existing code already addresses large grid-scale systems (Ordinance 2899); the council must now consider whether and how to permit midscale systems in commercial and industrial zones and how to treat residential batteries.

Key points from the briefing and discussion:
- PSE’s regional outlook: Nahn said the utility estimates roughly 1,500 megawatts of storage may be needed by 2030 to integrate renewables. She discussed PSE demonstration and microgrid projects — including a small microgrid on Samish Island (described as a roughly 50-kilowatt system with about 332 kWh of storage) and a 2-megawatt Glacier site — and said PSE is pursuing both utility-owned and developer-owned models for storage sited near rooftop solar and other generation.
- Zoning/use cases: Windisch said the city adopted Ordinance 2899 last year to regulate large-scale BESS and is now calling the next phase “BESS 2.0,” which will consider midscale systems that could be allowed in commercial and industrial zones, plus residential systems that might be outright permitted with thresholds tied to model codes.
- Fire, code and permit requirements: Sumner staff noted the city has adopted the 2021 International Fire Code (IFC), which added provisions for energy storage systems. Staff called out a 600 kilowatt-hour IFC threshold that triggers hazard mitigation analysis, installed fire suppression designs and an emergency management plan during plan review. Reviewers will rely on building and fire codes, UL listing and third-party testing to evaluate systems during permitting.
- Emergency response and hazards: Bill Sandlin, assistant chief and fire marshal for East Pierce Fire and Rescue, described the fire district’s growing experience with exterior, cabinet-style storage arrays and said engines will respond with commercial response protocols, exposure protection and hydraulic analysis for water supply. Sandlin emphasized coordination with neighboring jurisdictions and use of plume forecasting and on-site alarm/detection systems to guide response. He said larger exterior arrays are designed with separated modules to contain thermal runaway to an isolated module or “tower.”
- Chemistry and alternatives: Council members asked about alternatives to lithium-ion chemistry. PSE and the on-call safety consultant, Chris Green, said lithium-ion is dominant now but other chemistries (for example sodium-ion and flow batteries such as vanadium flow types) are being deployed and may reduce some lifecycle impacts.
- Next steps and planning process: Windisch said staff hopes to bring draft code language and a planning commission discussion in the spring (target: May) to consider midscale definitions, performance standards and where systems should be allowed. Staff will consult fire reviewers and other jurisdictions and factor PSE’s evolving siting plans into recommendations.

Council members repeatedly asked for more fiscal and operational details (for example, how projects are funded and how much costs will pass to customers); PSE said those specifics require follow-up and offered to provide additional materials and the utility’s integrated resource and project planning documents. Several council members also asked for model sites and lessons learned from other states; presenters cited examples from California, Texas and Arizona and described national and statewide fire-chief networks that share incident and lesson reports.

What was not decided: The session was informational; council gave staff direction to continue research and to return to the planning commission with code options. No ordinance changes or formal votes were taken at the study session.

The city will continue coordinating permit-review expectations with East Pierce Fire and Rescue and expects to present draft land-use approaches for midscale and residential energy storage to the planning commission in coming months.