Insurance and Financial Responsibility
What King County requires
Ordinance 19824 sets a flat $1 million financial responsibility threshold for BESS facilities with thermal runaway risk, regardless of facility size or location. A 2 MWh system and a 520 MWh facility have the same floor.
What that costs
Financial responsibility bonds are priced at roughly 30-40 cents per $100 of insured value. A $1 million bond costs about $3,000-4,000 per year. On a $100M+ project, that is negligible.
What facility insurance costs
Lithium-ion BESS facility insurance runs 0.3-1.2% of total project value annually. For a $100M facility, that’s $300,000-1.2 million per year. Pricing depends on battery chemistry, system design, monitoring, spacing between units, and fire department coordination.
Sodium-ion insurance rates have not been published yet. Insurers need several years of operational data before setting rates for a new technology. Based on the lower risk profile (no thermal runaway, passive cooling), rates are expected to be lower once data accumulates.
The insurance market after Moss Landing
Vistra wrote off $400 million from the Moss Landing fire (January 2025) and expects to recover a significant portion through property damage and business interruption insurance. Despite this, industry insurers characterize Moss Landing as “impactful but not defining,” and rates have remained stable at 30-40 cents per $100 of insured value.
What is changing:
- Standard liability policies exclude pollution and environmental contamination. That coverage must be purchased separately.
- Indoor NMC (nickel-manganese-cobalt) installations: many underwriters are reluctant or refusing coverage.
- Insurers are requiring more documentation before writing policies: UL 9540A fire testing proof, thermal management plans, fire department pre-incident coordination.
How this compares to actual cleanup costs
| Incident | Facility Size | Estimated Cleanup Cost |
|---|---|---|
| Moss Landing, CA (2025) | 300 MW | Tens of millions (EPA-ordered, ongoing). Vistra $400M writeoff. |
| Gateway, San Diego (2024) | 250 MW | EPA-ordered cleanup, cost not yet public |
King County’s $1 million threshold would not cover a fraction of either cleanup.
Sources
- Beyond the headlines: The BESS insurance market after Moss Landing (Energy-Storage.News)
- Battery energy storage systems insurance (Amwins)
- Battery storage insurance requirements in 2026 (Solarif)
- Battery storage insurance cost and coverage (Elemental Risk Management)