What We're Asking

PSE needs grid storage. Washington’s CETA targets require it, and the Mt. Si substation next door makes this a reasonable site. We get that. We’re not trying to kill this project.

But we think the community has a right to ask for two specific things.

1. Sodium-ion or equivalent non-lithium-ion chemistry

Jupiter Power’s own $500M Peak Energy contract tells you where the industry is headed. Sodium-ion gets rid of:

Thermal runaway — the mechanism behind every major BESS fire
Hydrogen fluoride and heavy metal emissions
Round-the-clock cooling fan noise (sodium-ion uses passive cooling)

The facility won’t be operational until late 2028. Sodium-ion will be commercially available before then.

2. Tree retention on the west (Parkway-facing) side

Critical area buffers protect the north and east edges. The west side — facing the backyards of homes on Bracken Place SE and SE Center Street — has nothing. The trees are already there. Leaving them alone costs Jupiter Power nothing and preserves the visual buffer between the facility and the neighborhood.

Proposed changes to King County’s BESS ordinance

We’ve also proposed two amendments to Ordinance 19824 that would apply county-wide, not just at this site:

Add battery chemistry to the alternatives analysis (Condition 29). The ordinance already requires applicants to evaluate alternative locations and demand management strategies. It should also require them to explain why they’re not using a safer chemistry when one is commercially available. This doesn’t ban lithium-ion — it requires the applicant to justify the choice.
Scale the financial responsibility threshold (Section 17.B). Right now the ordinance sets a flat $1 million regardless of facility size or location. A 2 MWh system in an industrial park and a 520 MWh facility across from a residential neighborhood have the same liability floor. The proposed amendment ties the amount to capacity and adjusts for proximity to homes and sensitive habitat.

Both of these build on what’s already in the ordinance. The ordinance itself (Section 19) requires a study report by approximately September 2027 evaluating whether the financial responsibility thresholds are adequate and whether technology changes warrant updates. We think that evaluation shouldn’t wait — the gaps are clear now, and projects are already in the pipeline.

We’ve shared these proposals with Councilmember Perry’s office. We’ll update this page as that conversation develops.