Off-grid solar in Montana
In Montana's darkest month, December, panels tilted toward the sun get about 2.5 peak sun hours a day, from 1.6 to 2.7 depending on where you are. Sized for that, a typical off-grid home needs about 17 panels and 4 batteries; a cabin, 4 panels and 1 battery. Flat panels, like on a van roof, get 49% less that month.
Answer a few taps in a guide and every page like this shows the numbers for your own setup. Start
Every setup, sized for Montana
Each guide's usual answers, with Montana's December sun. Tap one to change the answers to yours.
| Setup | Panels | Batteries | About |
|---|---|---|---|
| Off-grid home | 17 × 410 W | 4 | $10,000 – $12,000 |
| Backup for my house | 4 × 410 W | 2 | $9,000 – $11,500 |
| Tiny house | 8 × 410 W | 2 | $6,000 – $7,500 |
| Cabin or shed | 4 × 410 W | 1 | $4,000 – $5,000 |
| RV, bus or skoolie | 8 × 410 W | 2 | $6,000 – $7,500 |
| Van | 4 × 200 W | 3 | $6,000 – $7,500 |
| Just emergencies or camping | 4 × 200 W | Power station | $3,500 – $4,500 |
Van and RV numbers use flat-roof sun (1.3 h) and are capped by roof space, so they lean on driving and a generator in December. Costs are the gear only.
Sun in Montana, month by month
Tilted at latitude Flat. December gets 38% of the sun of the brightest month (6.5 h). Size for December and the rest of the year has spare.
Across Montana
Darkest-month sun differs by place. The 10 ZIP areas range from 1.6 hours in the 599xx ZIP area to 2.7 in the 593xx ZIP area. That's 74% more panel output for the same panels.
Common questions
How many solar panels do I need to live off grid in Montana?
Sized for Montana's darkest month (December, about 2.5 peak sun hours on tilted panels), a typical off-grid home needs about 17 panels (410 W each) and 4 server-rack batteries; a cabin about 4 panels and 1 battery. Your own loads change this; the guides size it for you.
How many peak sun hours does Montana get in winter?
About 2.5 a day in December on panels tilted at latitude, and 1.3 on flat panels (NASA POWER, at the state's center of population), ranging from 1.6 in the 599xx ZIP area to 2.7 in the 593xx ZIP area.
Does off-grid solar work in Montana in winter?
Yes, if it's sized for December: that month gets about 38% of the sun of the brightest month, so a system sized for December has plenty the rest of the year.
Data: NASA Langley Research Center POWER Project, long-term monthly averages at Montana's 2020 Census center of population and at each 3-digit ZIP area. Method and downloads.