What Wire Gauge for the Battery-to-Inverter Cable?
The battery-to-inverter cable is the highest-current wire in a van, so getting it right matters for safety. Two independent checks decide the gauge, and you use the thicker of the two:
- Ampacity. The wire must safely carry the fuse rating. We use the ABYC E-11 105°C table for cable outside the engine space.
- Voltage drop. The wire must keep voltage drop under 3% over the round-trip length (both the positive and negative runs), or the inverter browns out under load.
Worked example
A 1,000 W inverter at 12V draws about
1000 ÷ 12 ÷ 0.9 = 92.6 A continuously. Fuse that at
ceil(92.6 × 1.25) = 125 A. The smallest ABYC 105°C conductor rated
for 125 A is 4 AWG (160 A), and 4 AWG also holds voltage drop
under 3% over a 5 ft (10 ft round-trip) run — so the answer is
4 AWG with a 125 A fuse.
| Inverter | Current | Fuse | Cable (one-way) | Wire |
|---|---|---|---|---|
| 1,000 W | 93 A | 125 A | 5 ft | 4 AWG |
| 2,000 W | 185 A | 250 A | 5 ft | 1/0 AWG |
| 3,000 W | 278 A | 350 A | 3 ft | 3/0 AWG |
Longer runs push the gauge up for voltage drop even when ampacity would allow thinner wire — always measure your actual cable path and double it for the round trip. The fuse protects the wire, so it must never exceed the wire's ampacity. Enter your own inverter size and cable length below to size it exactly.
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