3 AWG voltage drop at 300 feet
Computed voltage drop for 3 AWG copper conductors on a 300 ft one-way run.
11.76 V
drop on 3 AWG copper, 300 ft one-way, 80 A load · 9.8% of 120 V · 4.9% of 240 V
3 AWG at 300 ft by load
| Load | Drop | % at 120 V | % at 240 V | 3% rule (240 V) |
|---|---|---|---|---|
| 20 A | 2.94 V | 2.5% | 1.2% | OK |
| 40 A | 5.88 V | 4.9% | 2.5% | OK |
| 60 A | 8.82 V | 7.3% | 3.7% | OK at 240 V up to 5% |
| 80 A | 11.76 V | 9.8% | 4.9% | 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 · 250 ft
FAQ
What is the voltage drop on 3 AWG wire at 300 feet?
At 80 A (80% of its 100 A 75°C rating) 3 AWG copper drops 11.76 V over 300 ft one-way: 9.8% at 120 V or 4.9% 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.