Off-grid site report
Sonoma County, CA
38.3287, -122.7080 · 105 ft elevationRead this before you act on anything below. This is my researched starting point for Sonoma County, CA, not legal advice and not a guarantee. Rules change, and the deciding facts on any specific parcel (setbacks, perc results, overlay districts, deed restrictions, road frontage) live at the county or town office, not in any database. Before you buy land or build, confirm the current rules directly with the local zoning and health offices - the sources on this page tell you exactly who to call.
The local rulesSonoma County, CA
Zoning & raw-land occupancy
RestrictedIn unincorporated Sonoma County, Permit Sonoma administers zoning under Chapters 26 and 26C of the county code, which set rural density limits (like one dwelling unit per 60 acres in some zones). You can't just camp or occupy raw land as your residence; you generally need an approved dwelling and permit. source
Dwellings, tiny homes & RVs
RestrictedPermit Sonoma's Policy 8-1-1 lays out a permit path for temporary occupancy of RVs, travel trailers, and tiny homes (Transportable Housing Units), but it requires code-compliant electrical/plumbing hookups and septic or sewer connection, and most non-caregiver, non-fire-rebuild uses are treated as temporary rather than a right to live full-time in an RV or tiny home alone.
Building permits & codes
RestrictedNew dwellings on vacant or undeveloped parcels go through Permit Sonoma's standard zoning and building permit process, including environmental review. I did not find any confirmed county exemption from standard California Building Code requirements for off-grid or primitive dwellings, so ask Permit Sonoma directly if you're planning something unconventional.
Septic & composting toilets
RestrictedPermit Sonoma runs its own Onsite Wastewater Treatment System (OWTS) program under Sonoma County Code Sections 24-33 and 24-34, working under state oversight from the Water Resources Control Board. The county's own soils are called out as notoriously poor for septic, and a composting-toilet-only setup without any septic system is not confirmed as an approved standalone option, so check directly with Permit Sonoma's Well and Septic Division.
Greywater reuse
Generally allowedPermit Sonoma has delegated authority from the Regional Water Quality Control Board to regulate greywater in the unincorporated county, and recognizes three tiers of greywater systems with their own permit requirements. Simple clothes-washer systems may fall under a state plumbing code exemption, but confirm the specifics with Permit Sonoma's Graywater Program. source
Rainwater harvesting
Generally allowedPermit Sonoma's guidelines say rainwater catchment systems should meet California Plumbing Code chapters 15 and 16, and the county even provides a formula for estimating usable rainwater volume for development water-supply assessments. There's no standalone ordinance found that restricts simple residential rain collection.
Private wells & water rights
RestrictedPermit Sonoma's Well and Septic Division issues water well permits, and the county updated its Well Ordinance in 2023, adding dry-weather testing requirements for new dwellings in marginal or scarce water zones and metering/monitoring obligations for many well permit holders. Given the county's noted poor soils, siting a well alongside septic on raw land can be tricky, so this is worth a direct call to the Well and Septic Desk.
Living disconnected from utilities
Unclear - verifyI did not find a standalone Sonoma County provision allowing a permanent, fully utility-disconnected primary residence. The RV/tiny-home occupancy policy explicitly requires code-compliant electrical and plumbing connections plus septic or sewer (or a pump-and-haul contract), so full off-grid disconnection seems to only fit within narrow permitted categories like caregiver units or fire-rebuild situations. Confirm your specific plan with Permit Sonoma.
Sun30-year normals
- Peak-sun hours, annual average
- 5.4 hrs/day
- Worst month (sizes an off-grid array)
- 3.3 hrs/day
- Yearly output per 1 kW of panels
- 1,523 kWh
JFMAMJJASOND
Weather1991-2020
- Precipitation
- 27 in/yr
- Snowfall
- 0 in/yr
- Heating degree days
- 2,825 (mild)
- Frost-free season
- Feb 25 to Nov 29
How far help isstraight-line
- Hospital
Santa Rosa Memorial Hospital - 8.0 mi
- Fire station
CAL FIRE Sonoma Lake Napa Unit - Santa Rosa - 8.5 mi
- Hardware store
Lowe's - 0.6 mi
- Grocery
Oliver's Market - 0.5 mi
From OpenStreetMap. Road miles will be longer, often much longer in hill country.
Plan this spot
These open with this location's real numbers already filled in (ZIP 94931).
Size a solar systemHeat loss & insulationFirewood per winterRainwater harvestGarden sizePanel tilt
Looking at a specific parcel in Sonoma County, CA?The rules above are the jurisdiction. The land check runs the parcel itself: flood zone, soils and septic suitability, wetlands, slope, access, climate, and these verdicts, from a parcel number or coordinates.
Check a parcel →Share or save this report:New report
Sources: US Census Bureau geocoder; NLR PVWatts v8 (solar); NOAA NCEI 1991-2020 climate normals (nearest station) or Open-Meteo (ZIP-centroid) for weather; Open-Elevation; OpenStreetMap contributors. Public data retrieved Aug 22, 2026; agencies update their layers on their own schedules. Planning data, not a survey or legal advice.
New here, or not sure where this fits? Start here walks through the whole thing in order.