Off-grid solar in California
In California's darkest month, December, panels tilted toward the sun get about 4.1 peak sun hours a day, from 2.9 to 5.0 depending on where you are. Sized for that, a typical off-grid home needs about 11 panels and 4 batteries; a cabin, 4 panels and 1 battery. Flat panels, like on a van roof, get 37% 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 California
Each guide's usual answers, with California's December sun. Tap one to change the answers to yours.
| Setup | Panels | Batteries | About |
|---|---|---|---|
| Off-grid home | 11 × 410 W | 4 | $9,000 – $11,000 |
| Backup for my house | 4 × 410 W | 2 | $9,000 – $11,500 |
| Tiny house | 5 × 410 W | 2 | $5,500 – $7,000 |
| Cabin or shed | 4 × 410 W | 1 | $4,000 – $5,000 |
| RV, bus or skoolie | 6 × 410 W | 2 | $5,500 – $7,000 |
| 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 (2.6 h). Costs are the gear only.
Sun in California, month by month
Tilted at latitude Flat. December gets 54% of the sun of the brightest month (7.5 h). Size for December and the rest of the year has spare.
Across California
Darkest-month sun differs by place. The 57 ZIP areas range from 2.9 hours in the 960xx ZIP area to 5.0 in the 919xx 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 California?
Sized for California's darkest month (December, about 4.1 peak sun hours on tilted panels), a typical off-grid home needs about 11 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 California get in winter?
About 4.1 a day in December on panels tilted at latitude, and 2.6 on flat panels (NASA POWER, at the state's center of population), ranging from 2.9 in the 960xx ZIP area to 5.0 in the 919xx ZIP area.
Does off-grid solar work in California in winter?
Yes, if it's sized for December: that month gets about 54% 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 California's 2020 Census center of population and at each 3-digit ZIP area. Method and downloads.