Off-grid site report

Custer County, MT

46.3972, -105.8183 · 2,438 ft elevation

Read this before you act on anything below. This is my researched starting point for Custer 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 rulesCuster County, MT

Zoning & raw-land occupancy

RestrictedCuster County has adopted a countywide zoning resolution allowing farming, ranching, one dwelling, and accessory buildings by right; other uses need a Special Use Permit or PUD, and setbacks scale with parcel size. source

Dwellings, tiny homes & RVs

Unclear - verifyThe county addresses RV storage and mobile home moves (Treasurer sign-off required), but has not confirmed adoption of the state's Appendix Q/AQ tiny house code; ask Planning and Zoning directly. source

Building permits & codes

Varies locallyCuster County has not adopted a countywide building code; state electrical, plumbing, and septic codes apply instead, but a zoning permit is still required before construction. source

Septic & composting toilets

Generally allowedThe county administers its own On-Site Wastewater Treatment System (OWTS) regulations layered on state DEQ standards; cesspools and seepage pits are banned, and an approved system is required for occupancy. source

Greywater reuse

RestrictedGreywater must ultimately be disposed of through a compliant wastewater treatment system under the state subsurface wastewater standards the county has adopted; no separate reuse exemption was found. source

Rainwater harvesting

Unclear - verifyNo Custer County ordinance addressing rainwater harvesting was found; this defaults to Montana's general state framework.

Private wells & water rights

Generally allowedWell permitting is a state DNRC/DPHHS matter; the county's OWTS rules require setbacks from wells and sometimes testing during subdivision review, but the county does not itself regulate well permitting. source

Living disconnected from utilities

Unclear - verifyNo explicit county rule requires grid electrical connection, but any structure with piped water must connect to an approved wastewater system or public sewer under county OWTS rules. source

Open the full county page with sources →

Sun30-year normals

Peak-sun hours, annual average: 4.8 hrs/day
Worst month (sizes an off-grid array): 2.6 hrs/day
Yearly output per 1 kW of panels: 1,385 kWh

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Weather1991-2020

Precipitation: 12 in/yr
Snowfall: 30 in/yr
Heating degree days: 7,639 (severe)
Frost-free season: May 8 to Sep 29

How far help isstraight-line

Hospital Holy Rosary Health Center: 0.5 mi
Fire station Custer County Fire Department: 0.9 mi
Hardware store Steadman's Ace Hardware: 0.4 mi
Grocery Walmart Supercenter: 0.4 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 59301).

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.