Off-grid site report

Washington County, MO

37.9248, -90.7739 · 948 ft elevation

Read this before you act on anything below. This is my researched starting point for Washington County, MO, 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 rulesWashington County, MO

Zoning & raw-land occupancy

Unclear - verifyWashington County itself does not require permitting for sites outside the city limits of Potosi, per the county's own economic-development page. Incorporated towns like Potosi, Caledonia, Irondale, and Mineral Point set their own zoning rules. source

Dwellings, tiny homes & RVs

Unclear - verifyNo Washington County ordinance on dwelling size, tiny homes, or RV residency was found. This likely falls to individual town ordinances if inside city limits, and is otherwise unregulated at the county level.

Building permits & codes

Varies locallyNo countywide building code is adopted per Missouri state data; building permits are handled town by town, such as Potosi's Building Inspector process. Confirm with the relevant city if your land is inside municipal limits. source

Septic & composting toilets

RestrictedThe Washington County Health Department issues OWTS (septic) construction permits under Missouri DHSS's statewide minimum standards. This applies regardless of whether you're inside or outside a town. source

Greywater reuse

Unclear - verifyNo Washington County or Missouri DHSS/DNR policy specific to greywater reuse was confirmed. Ask the county health department directly before installing a greywater system.

Rainwater harvesting

Generally allowedNo Washington County ordinance limiting rainwater collection was found, so the general state allowance for collecting and using rainwater applies.

Private wells & water rights

RestrictedWell construction statewide is governed by Missouri DNR's Well Construction Rules, while the Washington County Health Department supports well water testing and recommends annual testing.

Living disconnected from utilities

Generally allowedWith no countywide permitting requirement outside Potosi's city limits, living off-grid faces fewer local barriers here, though septic and well rules still apply regardless of utility hookups.

Open the full county page with sources →

Sun30-year normals

Peak-sun hours, annual average: 5.0 hrs/day
Worst month (sizes an off-grid array): 3.7 hrs/day
Yearly output per 1 kW of panels: 1,368 kWh

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Weather1991-2020

Precipitation: 44 in/yr
Snowfall: 15 in/yr
Heating degree days: 4,958 (moderate)
Frost-free season: Apr 14 to Oct 24

How far help isstraight-line

Hospital Washington County Memorial Hospital: 0.1 mi
Fire station Potosi Fire Station: 0.6 mi
Hardware store Dickey Bub Farm And Home: 0.4 mi
Grocery Walmart Supercenter: 0.1 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 63660).

Size a solar system Heat loss & insulation Firewood per winter Rainwater harvest Garden size Panel tilt

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.