San Mateo County, CA Outdoor Lighting: Dark Sky Rules (2026)

Outdoor lighting standards in unincorporated San Mateo County combine zoning requirements (glare control and light trespass prohibitions in the zoning regulations), California Energy Code Title 24 Part 6 §140.7 (outdoor lighting power density caps by lighting zone), and LCP policies in the Coastal Zone (dark skies and habitat protection, especially in Pescadero/Año Nuevo where seabird disorientation is a concern). Key requirements: exterior lighting must use fully shielded (full-cutoff or FCU) fixtures that emit no light above the horizontal plane through the fixture; light must be directed downward; light trespass onto adjacent residential property measured at the property line should generally be less than 0.5 foot-candles (industry standard); LED color temperature should be 3000K or lower to reduce sky glow and impact on wildlife; motion-sensor security lighting is encouraged over continuous illumination. Commercial parking lot lighting must meet Title 24 power-density limits (LZ1-LZ4 zoning). In the Coastal Zone, lighting near seabird nesting areas (Pescadero Marsh, Año Nuevo) must be amber/red-shifted or shielded to prevent nocturnal disorientation of newly fledged seabirds. Streetlights in unincorporated areas are typically LED conversions at 3000K operated by the County or PG&E.