How far can you run 4/0 AWG wire?

At 20 A on a 120 V single-phase circuit, 4/0 AWG copper stays under 3% voltage drop for about 1476 ft one-way. At 240 V the same load reaches roughly 2952 ft, because allowable drop scales with system voltage.

What is the voltage drop of 4/0 AWG wire per 100 feet?

About 0.24 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 4/0 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.

4/0 AWG Voltage Drop — Max Run Length by Load

Voltage drop for 4/0 AWG copper and aluminium: at 20 A on 120 V single phase the 3% limit is reached at about 1476 ft one-way. Full table by load, voltage and distance.

Quick answer

4/0 AWG copper reaches 3% voltage drop at about 1476 ft one-way carrying 20 A on a 120 V single-phase circuit. At 100 ft the same load drops 0.24 V (0.2%), calculated as VD = 2 × K × I × L / cmil with K = 12.9 for copper and 211,600 circular mils.

3% limit @ 20 A, 120 V

1476ft

3% limit @ 20 A, 240 V

2952ft

Drop @ 100 ft, 20 A

0.24V

Ω / 1000 ft (Cu)

0.0490

Maximum one-way run length at 3% drop

Copper 4/0 AWG. Aluminium distances are roughly 62% of these figures.

Load	120 V 1Ø	240 V 1Ø	208 V 3Ø	480 V 3Ø
5 A	5,905 ft	11,810 ft	11,819 ft	27,275 ft
10 A	2,952 ft	5,905 ft	5,909 ft	13,637 ft
15 A	1,968 ft	3,936 ft	3,939 ft	9,091 ft
20 A	1,476 ft	2,952 ft	2,954 ft	6,818 ft
25 A	1,181 ft	2,362 ft	2,363 ft	5,455 ft
30 A	984 ft	1,968 ft	1,969 ft	4,545 ft
40 A	738 ft	1,476 ft	1,477 ft	3,409 ft
50 A	590 ft	1,181 ft	1,181 ft	2,727 ft
60 A	492 ft	984 ft	984 ft	2,272 ft
80 A	369 ft	738 ft	738 ft	1,704 ft
100 A	295 ft	590 ft	590 ft	1,363 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	0.03%	0.04%	0.05%	0.08%
50 ft	0.05%	0.08%	0.1%	0.15%
75 ft	0.08%	0.11%	0.15%	0.23%
100 ft	0.1%	0.15%	0.2%	0.3%
150 ft	0.15%	0.23%	0.3%	0.46%
200 ft	0.2%	0.3%	0.41%	0.61%
300 ft	0.3%	0.46%	0.61%	0.91%

Percent drop, 120 V single phase, copper.

Published standard

Frequently asked

How far can you run 4/0 AWG wire?: At 20 A on a 120 V single-phase circuit, 4/0 AWG copper stays under 3% voltage drop for about 1476 ft one-way. At 240 V the same load reaches roughly 2952 ft, because allowable drop scales with system voltage.
What is the voltage drop of 4/0 AWG wire per 100 feet?: About 0.24 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 4/0 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.

4/0 AWG Voltage Drop — Max Run Length by Load

Maximum one-way run length at 3% drop

Voltage drop by distance at common loads

Frequently asked

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