Off-grid site report

St. Charles County, MO

38.8019, -90.7194 · 610 ft elevation
Read this before you act on anything below. This is my researched starting point for St. Charles 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 rulesSt. Charles County, MO

Zoning & raw-land occupancy
RestrictedSt. Charles County adopted a countywide Unified Development Ordinance in 1999 covering all unincorporated land; living on raw land without a permitted structure/use isn't allowed. Incorporated cities have their own separate zoning. source
Dwellings, tiny homes & RVs
RestrictedThe county's Agricultural District sets an 800 sq ft minimum for single-family homes, RVs cannot be occupied as permanent residences or hooked to dedicated utilities, and generally only one dwelling unit is allowed per lot. source
Building permits & codes
RestrictedSt. Charles County has adopted its own building code (unlike the state, which has no statewide code), and permits/inspections are required for essentially all new residential construction. source
Septic & composting toilets
RestrictedThe county's Building and Code Enforcement Division directly permits OWTS (septic) systems, generally requiring three acres per dwelling (sometimes reducible to one with approval), and bans new lagoons outright. source
Greywater reuse
Unclear - verifyNot confirmed: no county, DNR, or DHSS rule specifically addresses greywater reuse. Check with the county's OWTS program before setting up a system.
Rainwater harvesting
Generally allowedNo county-specific restriction was found, so rainwater harvesting appears to follow Missouri's general permissive baseline.
Private wells & water rights
RestrictedNo dedicated county well program was found, so wells are likely regulated under Missouri's statewide Well Construction Rules via DNR; whether the county adds anything extra isn't confirmed. source
Living disconnected from utilities
RestrictedThe county's UDO bars occupying or supplying dedicated utilities to RVs used as residences, meaning off-grid living outside the normal building/septic/well permitting framework is not sanctioned for occupied dwellings. source

Open the full county page with sources →

Sun30-year normals

Peak-sun hours, annual average
4.9 hrs/day
Worst month (sizes an off-grid array)
3.3 hrs/day
Yearly output per 1 kW of panels
1,405 kWh
JFMAMJJASOND

Weather1991-2020

Precipitation
41 in/yr
Snowfall
16 in/yr
Heating degree days
4,983 (moderate)
Frost-free season
Apr 11 to Oct 24

How far help isstraight-line

Hospital
Progress West Hospital
6.1 mi
Fire station
O'Fallon Fire Protection District Station 3
1.9 mi
Hardware store
The Home Depot
1.3 mi
Grocery
Walmart Supercenter
1.0 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 63366).

Size a solar systemHeat loss & insulationFirewood per winterRainwater harvestGarden sizePanel tilt

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.