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Sonoma Water to replace aging rooftop solar with microgrid at 404 Aviation to secure 72‑hour backup power
Summary
Sonoma Water recommended and the board approved a microgrid services agreement to replace the 20‑year rooftop solar system at 404 Aviation Boulevard with a fixed‑tilt solar and battery system to provide 72 hours of isolated power for the building, reduce generator costs and save an estimated $900,000 over 20 years.
The Sonoma County Board of Supervisors approved a Sonoma Water recommendation to enter a microgrid services agreement to replace the aging rooftop array at 404 Aviation Boulevard with a solar‑plus‑battery microgrid.
Sonoma Water Principal Engineer Dale Roberts told the board the existing 20‑year system is near the end of its useful life, is high‑maintenance, and (under current interconnection rules) does not provide power when the grid is down. "Our emergency operations center requires reliable continuous power during grid outages," Roberts said, explaining the proposed system would enable the building to remain isolated from the utility for up to 72 hours without relying on a diesel standby generator.
The proposal calls for Scale Microgrids to finance, design, build, own, operate and maintain the new system while Sonoma Water purchases on‑site energy at a predictable price. Roberts said the 20‑year agreement shows net savings of more than $900,000 over time, avoids roughly $10,000 per year in standby‑generator O&M, and supports Sonoma Water’s resilience goals.
Why it matters: The county said the site now serves as an emergency operations center and needs continuous power during public‑safety power shutdowns, storms and fire seasons. A modern battery system would also reduce greenhouse‑gas reliance on diesel generators.
Board action: After a public hearing and brief public comment about generator safety, the board adopted the recommended findings under the cited government code and authorized the general manager of Sonoma Water to execute the microgrid services agreement and related documents, in form approved by county counsel.
Details and next steps: Staff will file a notice of exemption (replacement of an existing facility, not an expansion) and complete the PG&E interconnection and construction documents as needed. The staff presentation included a tariff analysis and an assumed 5% increase in grid costs versus a 3% escalation in the agreement pricing.
