1/0 AWG voltage drop at 25 feet
Computed voltage drop for 1/0 AWG copper conductors on a 25 ft one-way run.
0.73 V
drop on 1/0 AWG copper, 25 ft one-way, 120 A load · 0.6% of 120 V · 0.3% of 240 V
1/0 AWG at 25 ft by load
| Load | Drop | % at 120 V | % at 240 V | 3% rule (240 V) |
|---|---|---|---|---|
| 30 A | 0.18 V | 0.2% | 0.1% | OK |
| 60 A | 0.37 V | 0.3% | 0.2% | OK |
| 90 A | 0.55 V | 0.5% | 0.2% | OK |
| 120 A | 0.73 V | 0.6% | 0.3% | OK |
Vd = 2 × length × R × I ÷ 1000, R = 0.122 Ω/1000 ft (copper, NEC Ch. 9 Table 8). Aluminum is about 1.6× higher.
Same wire, other distances
50 ft · 75 ft · 100 ft · 125 ft · 150 ft · 200 ft · 250 ft · 300 ft
FAQ
What is the voltage drop on 1/0 AWG wire at 25 feet?
At 120 A (80% of its 150 A 75°C rating) 1/0 AWG copper drops 0.73 V over 25 ft one-way: 0.6% at 120 V or 0.3% at 240 V.
How far can I run 1/0 AWG at 120 amps?
To stay within 3% at 120 V, about 123 ft one-way; at 240 V about 246 ft.