1/0 AWG Voltage Drop — Max Run Length by Load
Voltage drop for 1/0 AWG copper and aluminium: at 20 A on 120 V single phase the 3% limit is reached at about 736 ft one-way. Full table by load, voltage and distance.
Quick answer
1/0 AWG copper reaches 3% voltage drop at about 736 ft one-way carrying 20 A on a 120 V single-phase circuit. At 100 ft the same load drops 0.49 V (0.41%), calculated as VD = 2 × K × I × L / cmil with K = 12.9 for copper and 105,535 circular mils.
3% limit @ 20 A, 120 V
736ft
3% limit @ 20 A, 240 V
1472ft
Drop @ 100 ft, 20 A
0.49V
Ω / 1000 ft (Cu)
0.0983
Maximum one-way run length at 3% drop
Copper 1/0 AWG. Aluminium distances are roughly 62% of these figures.
| Load | 120 V 1Ø | 240 V 1Ø | 208 V 3Ø | 480 V 3Ø |
|---|---|---|---|---|
| 5 A | 2,945 ft | 5,890 ft | 5,894 ft | 13,603 ft |
| 10 A | 1,472 ft | 2,945 ft | 2,947 ft | 6,801 ft |
| 15 A | 981 ft | 1,963 ft | 1,964 ft | 4,534 ft |
| 20 A | 736 ft | 1,472 ft | 1,473 ft | 3,400 ft |
| 25 A | 589 ft | 1,178 ft | 1,178 ft | 2,720 ft |
| 30 A | 490 ft | 981 ft | 982 ft | 2,267 ft |
| 40 A | 368 ft | 736 ft | 736 ft | 1,700 ft |
| 50 A | 294 ft | 589 ft | 589 ft | 1,360 ft |
| 60 A | 245 ft | 490 ft | 491 ft | 1,133 ft |
| 80 A | 184 ft | 368 ft | 368 ft | 850 ft |
| 100 A | 147 ft | 294 ft | 294 ft | 680 ft |
Source & method: Derived from VD = 2 × K × I × L / cmil (1.732 × K × I × L / cmil for three phase), solved for L at 3% of nominal voltage. Run your exact circuit.
Voltage drop by distance at common loads
| Distance | 10 A | 15 A | 20 A | 30 A |
|---|---|---|---|---|
| 25 ft | 0.05% | 0.08% | 0.1% | 0.15% |
| 50 ft | 0.1% | 0.15% | 0.2% | 0.31% |
| 75 ft | 0.15% | 0.23% | 0.31% | 0.46% |
| 100 ft | 0.2% | 0.31% | 0.41% | 0.61% |
| 150 ft | 0.31% | 0.46% | 0.61% | 0.92% |
| 200 ft | 0.41% | 0.61% | 0.81% | 1.22% |
| 300 ft | 0.61% | 0.92% | 1.22% | 1.83% |
Published standard — source: Voltage drop from the standard VD formula with trade K constants
Frequently asked
- How far can you run 1/0 AWG wire?
- At 20 A on a 120 V single-phase circuit, 1/0 AWG copper stays under 3% voltage drop for about 736 ft one-way. At 240 V the same load reaches roughly 1472 ft, because allowable drop scales with system voltage.
- What is the voltage drop of 1/0 AWG wire per 100 feet?
- About 0.49 V at 20 A on 120 V single phase, using VD = 2 × K × I × L / cmil with K = 12.9 for copper.
- Is 3% voltage drop a code requirement?
- It is a recommendation, not a mandatory limit, in most adopted codes: roughly 3% on the branch circuit and 5% total including the feeder. Some local amendments and specifications do make it enforceable, so check what applies to your job.
- Does aluminium change the 1/0 AWG numbers?
- Yes. Aluminium uses K = 21.2 instead of 12.9, so drop is about 64% higher for the same size and run, and allowable distance falls by roughly the same proportion.
More on 1/0 AWG
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