1/0 AWG Voltage Drop Chart
1/0 AWG copper wire has a resistance of 0.122 ohms per 1000 feet. NEC 240.4(D) and the standard ampacity tables cap this gauge at 150A for a branch-circuit breaker (60°C ampacity: 125A; 75°C: 150A). At 100 feet on a 120V circuit, it stays under 3% voltage drop up to about 147A.
1/0 AWG Wire Specifications
| Property | Value |
|---|---|
| Gauge | 1/0 AWG |
| Resistance (copper) | 0.122 Ω per 1000ft |
| Ampacity (60°C) | 125A |
| Ampacity (75°C) | 150A |
| NEC branch-circuit OCP | 150A |
| Amps that land on 3% drop at 100ft (120V) | ~147A |
Voltage Drop by Amps & Distance (120V)
Green = within the 3% branch-circuit drop target, Amber = 3-5% (past branch target, within 5% feeder+branch total), Red = past the 5% feeder+branch total recommendation
When to Use 1/0 AWG
Typical applications: Main service entrance, large commercial feeders, and industrial applications.
Under typical 75°C-termination assumptions, 1/0 AWG is commonly protected by up to 150A branch-circuit OCP. Real install ceilings depend on conductor and termination temperature ratings, cable type (NM-B is limited to the 60°C column in residential use, so the usable value is lower), NEC 310.15(C)(1) bundling adjustments, and NEC 310.15(B) ambient corrections. Even with ampacity margin, longer runs may fall outside the 3% branch-circuit drop target recommended in NEC 210.19(A) Informational Note 4, which is why the distance table above matters.