Copper 1/0 AWG wire, which most sellers label 0 gauge, is rated 125 A at 60°C, 150 A at 75°C, and 170 A at 90°C in the NEC’s Table 310.16.
For the full breakdown, see our best Zero Gauge Wire guide.
A spool marked “0 gauge” is almost always 1/0 AWG once you read the jacket, and that gap between label and marking is why quoted amp figures for the same cable run from 100 A to 300 A.
Strip the sales copy away and the deciding factors behind 0 gauge wire ampacity come down to three things: the metal, the temperature rating of the insulation and terminals, and the conditions of the install. Copper 1/0 AWG in building wire carries 125 A, 150 A, or 170 A depending on which column applies, before derating. Watts are separate arithmetic: 150 A equals 1,800 W at 12 V and 18,000 W at 120 V. The table below sorts copper against aluminum, and the sections after it cover what drags those numbers down.
What Does 0 Gauge Wire Mean In AWG Sizes?
Sizes above 1 AWG are spoken in “oughts,” so 1/0 AWG is said aloud as “one-ought” — the retail label 0 gauge comes straight from that. The NEC ampacity tables list the size as 1/0 AWG.
The marking printed on the jacket is the part worth trusting. A listing that advertises 0 gauge with no AWG or kcmil figure tells you nothing checkable about strand count, insulation, or temperature rating.
One wrinkle matters for anyone wiring a vehicle. Battery cable, welding lead, and car-audio power wire all get sold as 0 gauge with finer strands and different insulation, and those installs follow manufacturer instructions plus marine or automotive standards rather than Table 310.16. Treat the building-wire numbers here as context, not the rule that governs your run.
0 Gauge Ampacity Ratings: What Changes The Number
Metal, temperature rating, ambient heat, and conductor count are the four levers, and the lowest-rated termination sets the ceiling for the whole run. A “300 amp” claim on a retail listing describes a short burst on flexible cable, not continuous ampacity inside a wall.
| Conductor (1/0 AWG) | Termination And Insulation Rating | Allowable Ampacity |
|---|---|---|
| Copper | 60°C | 125 A |
| Copper | 75°C | 150 A |
| Copper | 90°C | 170 A |
| Copper, 90°C wire on 75°C lugs | Limited to 75°C column | 150 A |
| Aluminum or copper-clad aluminum | 60°C | 100 A |
| Aluminum or copper-clad aluminum | 75°C | 120 A |
| Aluminum or copper-clad aluminum | 90°C |