California Energy Code section 110.10 (2022) requires all newly constructed low-rise residential buildings to include a photovoltaic system sized to offset estimated annual electricity consumption. In Marin County (climate zone 3, southern climate zone 4 at higher elevations), typical sizing falls in the 3-6 kW range for a 2500-3500 sf home. Battery backup is not mandated but is increasingly common given wildfire-related PSPS events.