Off-Grid Builds: a camper van electrical system
A 12V van build sized around a compressor fridge, fan, lights and laptop, with roof solar and a 1,000W inverter.
Published · Updated
For about 1,100 Wh a day, our sample van uses 3 × 12V 100Ah LiFePO4 (3,840 Wh), 400W of roof solar, a Victron 100/50 MPPT, a 1,000W inverter and a battery monitor.
- About 1,100 Wh/day of example loads.
- Roof space limits solar; 400W is a common fit.
- Many vans add DC-DC charging from the alternator.
The load list
Example loads; replace them with yours in the Power Planner.
| Device | Watts × hours | Wh/day |
|---|---|---|
| 12V compressor fridge (example) | ≈25 W average × 24 h | 600 |
| Roof fan | 20 W × 8 h | 160 |
| LED lights | 20 W × 5 h | 100 |
| Laptop and phones | 80 W × 3 h | 240 |
| Total | 1,100 |
Sizing math
Battery: 1,100 Wh/day × 2 day(s) of autonomy ÷ 0.92 inverter ÷ 0.80 usable ≈ 2,989 Wh (0.92 from the NREL PVWatts manual, 0.80 from Victron LiFePO4 data). 3 × 12V 100Ah LiFePO4 batteries (1,280 Wh each: 12.8V × 100Ah) give 3,840 Wh as a 12V bank. See how to size a battery bank.
Solar: 1,100 Wh ÷ (4 peak sun hours × 0.77, the PVWatts V1 derate) ≈ 357 W of panels. We use 400W. Check your site's sun hours in NREL PVWatts and size for your worst month. See solar panel sizing.
Controller: Victron rates the SmartSolar 100/50 for 700W of nominal PV power on a 12V battery, so 400W fits with room to add a panel.
Inverter: 1,000W covers a laptop and small kitchen gadgets. A hair dryer or induction cooktop would need a 2,000W inverter and heavier cabling.
Parts list
The main parts. Size fuses, breakers and cable from each maker's manual and a wire-gauge table.
Renogy 12V 100Ah LiFePO4 battery (mini)
Compact 100Ah blocks; use three (check under-seat space against the maker's dimensions).
Check price on Amazon (opens in a new tab)
Victron SmartSolar MPPT 100/50
50A MPPT with Bluetooth monitoring.
Check price on Amazon (opens in a new tab)
Renogy P2 1000W pure sine inverter (12V)
1,000W pure sine inverter.
Check price on Amazon (opens in a new tab)
Victron SmartShunt 500A battery monitor
Battery monitor on the negative line.
Check price on Amazon (opens in a new tab)Wiring outline
Roof panels → roof gland → PV breaker → MPPT → fused bus bar → batteries. Add a DC-DC charger from the starter battery if you drive a lot. Inverter on its own fuse; a 12V fuse block feeds the fridge, fan and lights.
This is a planning outline, not a wiring diagram. Follow each manufacturer's manual, fuse every positive conductor close to the battery, and have a qualified installer check the work. Local codes apply to buildings and vehicles.
FAQ
Do I need a DC-DC charger?
If you want the engine to charge the house batteries, usually yes. Follow the battery and vehicle makers' guidance on charging lithium from an alternator.
Where do I go next?
Try the power planner to put numbers to your own situation, or see the product picks on the deals page.
Terms used here
- Watt (W)
- Rate of power use or production.
- Watt-hour (Wh)
- Energy: one watt for one hour.
- LiFePO4 (LFP)
- Lithium iron phosphate battery chemistry.
- Inverter
- Converts DC battery power to AC household power.
- MPPT
- Maximum power point tracking controller.
- Peak sun hours
- Hours of equivalent 1,000 W/m² sunlight per day.
- Derate
- Factor for real-world losses in solar output.
Sources
This guide is informational and based on published specifications and general references, not hands-on testing. Check the manufacturer's current specs before you buy.