RV & Van 12V Wire Size Chart (AWG) for Common Circuits
Getting wire gauge right is the single most important safety decision in a 12V van or RV build — undersized wire is the leading cause of electrical fires in DIY conversions. Here's a practical AWG reference for common circuits.
Get exact AWG for every run
The calculator does the voltage-drop math for your actual cable lengths and outputs a full wiring schedule — free.
Quick reference chart
| Circuit | Typical current | AWG (short runs) | Typical fuse |
|---|---|---|---|
| LED lights, USB outlets | 1-3A | 16-14 AWG | 5-10A |
| Water pump, vent fan | 3-8A | 14-12 AWG | 10-15A |
| 12V compressor fridge | 4-6A | 12-10 AWG | 15A |
| DC-DC charger (30-50A) | 30-50A | 8-6 AWG | 40-60A |
| 1,000W inverter | ~95A | 4-2 AWG | 100-125A |
| 2,000W inverter | ~190A | 2/0 AWG | 200-250A (Class T) |
| Main battery-to-bus-bar | varies | 2-4/0 AWG | match to bank/fuse |
"Short runs" means roughly under 10 feet round-trip. Every additional foot increases voltage drop — longer runs need the next size up, sometimes two sizes up.
Two things determine wire size — not just one
- Ampacity — the wire must carry the current without overheating. This is what most online charts show.
- Voltage drop — at 12V, even a small voltage loss is a large percentage. ABYC recommends ≤3% drop on critical/charging circuits and ≤10% on non-critical circuits (like interior lighting).
A wire can be rated for the current (ampacity OK) but still cause a 6% voltage drop on a 20-foot run — dimming lights and reducing charging current. That's why a simple "amps to AWG" table isn't enough for longer runs.
Use the right cable, not just the right gauge
Use fine-stranded, marine-grade tinned copper wire (rated for the marine/RV environment) rather than solid or automotive-grade wire — it resists vibration fatigue and corrosion. Crimp connections with a proper hydraulic crimper rather than soldering.
Worked example: 15-foot fridge run
A 12V fridge drawing 5A over a 15-foot one-way run (30 feet round-trip):
- At 10 AWG, voltage drop at 30 feet round-trip and 5A is close to the 3% threshold — borderline.
- Stepping up to 8 AWG keeps drop comfortably under 3%.
The calculator runs this math automatically for every circuit in your build, based on your actual cable lengths.
Fusing matches the wire, not the appliance
Whatever gauge you land on, the fuse protects that wire — sized at or below its safe ampacity, and at least 1.25× the load's continuous current. See fuse sizing for RVs for the full method.