Off-grid site report
Williamson County, IL
37.8136, -88.9369 · 404 ft elevationRead this before you act on anything below. This is my researched starting point for Williamson County, IL, 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 rulesWilliamson County, IL
Zoning & raw-land occupancy
Varies locallyWilliamson County has an adopted countywide Zoning Ordinance and map (since 2012, updated since) administered by the County Planning Department; rural districts generally allow one dwelling per five acres but rules differ by district. source
Dwellings, tiny homes & RVs
Varies locallyMobile/manufactured home placement rules differ by zoning district (allowed in some rural districts, not in 'rural estate'); no official county text was found on tiny homes or RV residency specifically, so confirm with Planning/Zoning. source
Building permits & codes
Generally allowedThe county maintains its own Building Permit Ordinance and application process, separate from municipal building departments in incorporated towns; a new statewide Illinois building code baseline also took effect January 1, 2025. source
Septic & composting toilets
Generally allowedSeptic and composting toilet systems require a permit through the Franklin-Williamson Bicounty Health Department, which administers Illinois's private sewage disposal code (IDPH, 77 Ill. Adm. Code 905) locally and may set standards at or above the state minimum. source
Greywater reuse
Unclear - verifyNo Williamson County or Bicounty Health Department page specifically addresses greywater reuse; this inherits state-level ambiguity and would likely be evaluated case-by-case, so ask Bi-County Environmental Health directly. source
Rainwater harvesting
Unclear - verifyNo official county or Illinois EPA/IDPH page specific to residential rainwater harvesting in Williamson County was found; not confirmed prohibited or permitted.
Private wells & water rights
Generally allowedPrivate well construction is permitted through the Franklin-Williamson Bicounty Health Department acting as IDPH's local agent, following the statewide well permitting and inspection process. source
Living disconnected from utilities
Unclear - verifyNo county ordinance explicitly addresses full grid-electric or municipal-water disconnection; occupancy likely depends on the county's building/occupancy requirements for water and waste systems rather than a specific electric-grid mandate. Confirm with County Building/Planning.
Sun30-year normals
- Peak-sun hours, annual average
- 5.0 hrs/day
- Worst month (sizes an off-grid array)
- 3.4 hrs/day
- Yearly output per 1 kW of panels
- 1,429 kWh
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Weather1991-2020
- Precipitation
- 49 in/yr
- Snowfall
- 14 in/yr
- Heating degree days
- 5,121 (moderate)
- Frost-free season
- Apr 16 to Oct 19
How far help isstraight-line
- Hospital
Herrin Hospital - 5.0 mi
- Fire station
Williamson County Fire Protection - 6.0 mi
- Hardware store
Menards - 4.8 mi
- Grocery
Walmart Supercenter - 4.9 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 62951).
Size a solar systemHeat loss & insulationFirewood per winterRainwater harvestGarden sizePanel tilt
Looking at a specific parcel in Williamson County, IL?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.