3 AWG voltage drop at 250 feet
Computed voltage drop for 3 AWG copper conductors on a 250 ft one-way run.
9.80 V
drop on 3 AWG copper, 250 ft one-way, 80 A load · 8.2% of 120 V · 4.1% of 240 V
3 AWG at 250 ft by load
| Load | Drop | % at 120 V | % at 240 V | 3% rule (240 V) |
|---|---|---|---|---|
| 20 A | 2.45 V | 2.0% | 1.0% | OK |
| 40 A | 4.90 V | 4.1% | 2.0% | OK |
| 60 A | 7.35 V | 6.1% | 3.1% | OK at 240 V up to 5% |
| 80 A | 9.80 V | 8.2% | 4.1% | OK at 240 V up to 5% |
Vd = 2 × length × R × I ÷ 1000, R = 0.245 Ω/1000 ft (copper, NEC Ch. 9 Table 8). Aluminum is about 1.6× higher.
Same wire, other distances
25 ft · 50 ft · 75 ft · 100 ft · 125 ft · 150 ft · 200 ft · 300 ft
FAQ
What is the voltage drop on 3 AWG wire at 250 feet?
At 80 A (80% of its 100 A 75°C rating) 3 AWG copper drops 9.80 V over 250 ft one-way: 8.2% at 120 V or 4.1% at 240 V.
How far can I run 3 AWG at 80 amps?
To stay within 3% at 120 V, about 92 ft one-way; at 240 V about 184 ft.