Voltage drop by wire size (50 A, 150 ft, 240 V)
| Copper wire | Drop (V) | Drop (%) | Within 3% |
|---|---|---|---|
| 8 AWG | 11.46 V | 4.78% | ✗ |
| 6 AWG | 7.37 V | 3.07% | ✗ |
| 4 AWG | 4.62 V | 1.93% | ✓ |
| 3 AWG | 3.67 V | 1.53% | ✓ |
| 2 AWG | 2.91 V | 1.21% | ✓ |
Voltage drop = 2 × 150 ft × 50 A × resistance ÷ 1000. Keeping it under 3% on branch circuits (5% total) is the NEC recommendation in the informational notes to 210.19 and 215.2.
Frequently asked questions
Is 8 AWG enough for 50 amps at 150 feet?
It carries 50 A, but at 150 ft the voltage drop is 4.8%. That is over 3%, so the next size up is recommended.
Does the distance include the return wire?
No. Enter the one-way distance; the formula already counts both conductors.