Over 100 feet one-way, 2 AWG copper drops 1.9% at 60A on 120V and 1.9% at 115A on 240V: loads up to 80A stay under 3% at 120V, and every load here up to 115A stays under 3% at 240V.
Single phase, copper conductor, one-way distance. ✅ = under 3%, ⚠️ = 3-5%, ❌ = over 5%
| Load | V-Drop | @ 120V | @ 240V |
|---|---|---|---|
| 60A | 2.3V | ✅ 1.9% | ✅ 1.0% |
| 80A | 3.1V | ✅ 2.6% | ✅ 1.3% |
| 100A* | 3.9V | ⚠️ 3.2% | ✅ 1.6% |
| 115A | 4.5V | ⚠️ 3.7% | ✅ 1.9% |
Longest one-way distance that keeps single-phase copper within 3%.
| Load | @ 120V | @ 240V |
|---|---|---|
| 60A | 155 ft | 310 ft |
| 80A | 115 ft | 230 ft |
| 100A | 95 ft | 185 ft |
| 115A | 80 ft | 160 ft |
* Above 95A, 2 AWG needs 75°C-rated terminations at both ends (NEC 110.14(C)); most breakers and panels rated 100A or less assume 60°C unless marked 75°C.
Voltage drop for single-phase circuits: Vdrop = 2 × I × R × L
Where I = current in amps, R = resistance per foot (0.000194 Ω/ft for 2 AWG copper, from NEC Chapter 9 Table 8 at 75°C), and L = one-way distance (100 ft).
The factor of 2 accounts for both the supply and return conductors. NEC recommends a maximum 3% voltage drop for branch circuits and 5% for the total circuit (feeder + branch).
If voltage drop is too high: Use the next larger wire size. Each single AWG step up in size cuts voltage drop by about 21% — it takes three steps to roughly halve it, since each step increases the conductor area by a factor of 1.26. Alternatively, for 120V loads, consider rewiring for 240V — same absolute drop but half the percentage.
It depends on the load and voltage. With NEC Table 8 resistance (0.194 Ω per 1000 ft at 75°C), a 100-foot run of 2 AWG copper drops 1.9% at 60A, 2.6% at 80A, 3.2% at 100A, 3.7% at 115A on 120V, and half those percentages on 240V. All of these meet the 3% branch-circuit guideline at 240V.
To stay within 3% voltage drop, 2 AWG copper can run about 155 ft at 60A on 120V, or 160 ft at 115A on 240V (one-way). Its maximum load is 115A at 75°C; lighter loads can run proportionally farther.
Upsize when your load pushes drop above 3%. At 115A on 240V over 100 feet, 2 AWG drops 1.9%; stepping up to 1 AWG cuts that to 1.5%. For motors, well pumps or sensitive electronics, aim for 2% or less.