Off-grid site report

Missoula County, MT

46.8948, -113.9668 · 3,393 ft elevation
Read this before you act on anything below. This is my researched starting point for Missoula County, MT, 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 rulesMissoula County, MT

Zoning & raw-land occupancy
Varies locallyMissoula County has both zoned and unzoned unincorporated areas requiring different permits (zoning compliance vs. land use permit); land inside Missoula city limits instead falls under the city's own Unified Development Code (Title 22). source
Dwellings, tiny homes & RVs
Unclear - verifyThe county has no confirmed formal tiny-home or ADU size category; new residential construction goes through standard building/zoning permits, and small accessory structures (under 200 sq ft, greenhouses, low decks, etc.) are exempt from building permits. Specific size thresholds cited on commercial sites are not confirmed officially.
Building permits & codes
RestrictedMissoula County requires building permits for single-family homes (it declined the state-allowed exemption), though commissioners have since exempted certain small structures; other permits (zoning, floodplain, plumbing, electrical, mechanical) may still apply even when building-permit exempt. source
Septic & composting toilets
Generally allowedThe Missoula City-County Health Department requires a septic permit before a building permit is issued, mandates approved toilet facilities for any occupied structure, and enforces a four-foot separation between drainfield and groundwater; composting toilets are not separately addressed in what I found. source
Greywater reuse
Unclear - verifyNo Missoula County-specific greywater ordinance was found; likely defaults to state DEQ baseline, but this is not confirmed, so ask the Health Department directly.
Rainwater harvesting
Unclear - verifyNo county or city-county health department page addressing rooftop rainwater collection was found; the general assumption is that state law does not prohibit personal non-potable use, but this is not confirmed locally.
Private wells & water rights
Generally allowedMost off-grid wells qualify as state-defined 'exempt wells' (10 acre-feet/year or less, 35 gpm or less) under DNRC rules, though starting in 2026 a Notice of Intent must be filed with DNRC before using a new exempt well; the county Health Department also reviews well siting during septic permitting. source
Living disconnected from utilities
Unclear - verifyNo ordinance explicitly requires grid electric connection, but any occupied structure must have an approved water source and wastewater system regardless of grid status, so full self-sufficiency still requires county sign-off on septic/well.

Open the full county page with sources →

Sun30-year normals

Peak-sun hours, annual average
4.4 hrs/day
Worst month (sizes an off-grid array)
1.8 hrs/day
Yearly output per 1 kW of panels
1,213 kWh
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Weather1991-2020

Precipitation
17 in/yr
Snowfall
50 in/yr
Heating degree days
7,349 (cold)
Frost-free season
May 17 to Sep 27

How far help isstraight-line

Hospital
Saint Patrick Hospital
2.1 mi
Fire station
East Missoula Rural Fire Department
2.0 mi
Hardware store
Liberty Safes of Montana
2.0 mi
Grocery
Missoula Farmer's Market
1.8 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 59807).

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

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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.