Off-grid site report

Williamson County, TN

35.9717, -86.6745 · 600 ft elevation

Read this before you act on anything below. This is my researched starting point for Williamson County, TN, 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, TN

Zoning & raw-land occupancy

RestrictedWilliamson County has a comprehensive zoning ordinance, adopted 2012 and effective 2013, that applies to all unincorporated land, unlike many rural TN counties with no zoning at all. This is a county-level rule set by the Williamson County Planning Department; incorporated cities have their own separate zoning. source

Dwellings, tiny homes & RVs

Unclear - verifyNo official Williamson County page spells out tiny-house-on-wheels or RV-as-permanent-dwelling occupancy standards. Codes Compliance handles mobile home setup and zoning enforcement and should be asked directly. source

Building permits & codes

RestrictedBuilding permits are required in unincorporated Williamson County through the county's Building Codes Division; the county has not opted out of standard permitting. Electrical permits now go through the State of Tennessee's core.tn.gov system as of 2023. source

Septic & composting toilets

RestrictedWilliamson County is a state-designated 'contract county' that runs its own septic permitting program via its Department of Sewage Disposal Management and Board of Health, which is more hands-on than counties that defer fully to TDEC. No dry-cabin or no-septic exemption was confirmed. source

Greywater reuse

Unclear - verifyNo Williamson County-specific greywater ordinance was found; this appears to inherit whatever ambiguity exists at the state level. Confirm directly with the county's Sewage Disposal Management office.

Rainwater harvesting

Generally allowedNo county-specific restriction on rainwater collection was found, so this inherits the general state position of no barrier to collection or use. Any plumbing tie-in would still go through the county Building Codes Division.

Private wells & water rights

Generally allowedWell drilling is regulated at the state level under the Tennessee Water Well Act of 1963, requiring a licensed driller, per the state Division of Water Resources. Tennessee does not mandate water testing for private wells. source

Living disconnected from utilities

Varies locallyNo county ordinance restricts disconnecting from the electric grid itself, but any habitable structure still triggers the county's building and septic permit requirements described above. 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): 3.4 hrs/day
Yearly output per 1 kW of panels: 1,382 kWh

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Weather1991-2020

Precipitation: 53 in/yr
Heating degree days: 4,107 (moderate)

How far help isstraight-line

Hospital Monroe Carell Jr. Children's Hospital at Vanderbilt: 13.6 mi
Fire station Brentwood Fire Station 4 Safety Center East: 2.8 mi
Hardware store Complete Home Hardware: 9.1 mi
Grocery Publix: 2.0 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 37135).

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 21, 2026; agencies update their layers on their own schedules. Planning data, not a survey or legal advice.