What Size Wire for 30 Amps at 150 Feet?
Voltage-drop-aware wire sizing for a 30-amp circuit running 150 ft (one-way) at 240V — because over distance, voltage drop, not ampacity, often sets the wire size.
Calculations are built on the 2023 National Electrical Code (NEC) and cross-checked against the published code tables. How we verify. Last reviewed June 2026.
Actual drop 2.9%. For ≤5% drop: 10 (4.5%).
Actual drop 1.9%. For ≤5% drop: 8 (4.7%).
At 150 ft, voltage drop governs: ampacity alone would allow 10 AWG copper, but staying ≤3% requires upsizing to 8.
Voltage Drop at 150 Feet
Voltage drop is calculated for a 240V single-phase circuit over a 150 ft one-way run (conductor length doubled for the return). Sizes meeting the ≤3% target are highlighted.
| Wire size | Copper drop | Aluminum drop | Within 3%? |
|---|---|---|---|
| 10 | 4.5% | 7.5% | — |
| 8 | 2.9% | 4.7% | |
| 6 | 1.8% | 3.0% | |
| 4 | 1.2% | 1.9% | |
| 3 | 0.9% | 1.5% | |
| 2 | 0.7% | 1.2% |
Drop % uses NEC Chapter 9, Table 8 DC resistance — an accepted approximation for typical power-factor AC branch circuits. The wire must also meet ampacity; both checks are applied above.
Different distance or voltage?
Open the calculator pre-filled with 30A, 240V, 150 ft to adjust material, temperature and drop target.