Solar PV systems involve high-voltage DC and substantial fault currents. Improper installation can cause fire, injury, or death. Consult a licensed electrician and your local Authority Having Jurisdiction (AHJ) before any installation work, and verify every value against the current NEC edition and current product datasheets. Numbers and recommendations on this page are educational starting points, not a substitute for professional design and inspection.
Van life
Solar setup for a van: the honest sizing math
Most DIY van builds run on 2–3 kWh/day — fridge, lights, fan, laptop, phone, and usually Starlink. That sets the size of every other component. Here's the recommended build, the numbers behind it, and where the corners are that will bite you if you cut them.
Typical van load profile
- 12V compressor fridge — 45W avg, 24h → ~1,080 Wh/day
- LED lights — 30W, 4h → 120 Wh
- Maxxair fan — 45W, 6h → 270 Wh
- Laptop + monitor — 95W, 5h → 475 Wh
- Phone + camera charging — 30W, 2h → 60 Wh
- Starlink — 65W avg, 6h → 390 Wh
Total: ~2.4 kWh/day base load. Heavy users with induction or AC push past 4–5 kWh/day.
Recommended build
Why these numbers
12V over 24V for vans, almost every time. It plays nicely with vehicle accessories (USB sockets, MaxxAir, water pump, fridge, lights — most are 12V native). The wire size penalty only starts hurting past 2 kW continuous draw, which vans rarely hit.
200Ah LFP gives you ~2.4 kWh usable (LFP allows full discharge, unlike AGM). That's about one day of base load with zero recharge — a healthy margin for cloudy stretches if you're parked and not driving.
400W of panels on a typical Sprinter/Transit/Promaster roof. At 4 peak sun hours/day average (national average), that's ~1,280 Wh/day after derating — adequate for the 2.4 kWh load if you also drive (DC-DC charging covers the gap). Driving a few hours a week makes any system more forgiving.
40A MPPT — for 400W at 12V the math is 400 ÷ 12 × 1.25 (NEC 690.8) = 41.7A minimum. A 40A controller is fine if panels are slightly derated; a 50A or 60A controller gives you headroom to expand later.
2000W inverter handles a microwave, induction burner, or coffee maker — the three appliances van builders most often want. Anything bigger means you should consider 24V.
Where it falls apart
- Cold weather charging. LFP refuses to accept charge below ~32°F. If you're winter camping, spec self-heating LFP or insulated battery enclosure.
- Stationary off-grid for >3 days. Without driving (no DC-DC input), 400W isn't enough in winter at northern latitudes. Either oversize panels to 600W+ or plan to drive every few days.
- Running AC. A typical 12,000 BTU rooftop AC pulls 1,200W continuous. With AC, you need 600W+ panels and 400Ah+ battery. Or just plan to plug in.