Ampacity by temperature rating
| Temperature rating | Ampacity | Typical insulation |
|---|---|---|
| 60°C | 125 A | — |
| 75°C | 150 A | THW |
| 90°C | 170 A | THHN / THWN-2, XHHW-2 |
Reference tables · Copper ampacity
2023 NEC · Table 310.16
1/0 AWG copper wire ampacity
At a 75°C termination rating, 1/0 AWG copper carries 150 A under the published table's basis conditions — 30°C ambient, no more than three current-carrying conductors.
What 1/0 AWG copper is used for
1/0 AWG copper carries 150 A at 75°C. Conductors this size are service entrance and main feeder conductors — the run between a meter and a panel, or between a main panel and a large subpanel. It pairs with a 150 A overcurrent device.
Terminations usually decide the practical answer. Breakers and equipment are typically listed for 60°C or 75°C, so even 90°C-rated insulation on this conductor is normally limited to the 150 A column at the terminals. Check the equipment's listing rather than assuming.
Derating
Ampacity in real conditions
| Ambient | 3 conductors | 4 conductors | 7 conductors | 10 conductors | 21 conductors |
|---|---|---|---|---|---|
| 20°C | 166.5 A | 133.2 A | 116.6 A | 83.3 A | 74.9 A |
| 30°C | 150 A | 120 A | 105 A | 75 A | 67.5 A |
| 40°C | 132 A | 105.6 A | 92.4 A | 66 A | 59.4 A |
| 50°C | 112.5 A | 90 A | 78.8 A | 56.3 A | 50.6 A |
Properties
| Circular mils | 105,600 |
|---|---|
| DC resistance | 0.122 Ω per 1000 ft |
| Ampacity at 75°C | 150 A |
| Overcurrent ceiling | Set by ampacity |
| Largest standard breaker | 150 A |
| Area, THHN / THWN-2 | 0.1855 in² |
| Area, XHHW-2 | 0.1825 in² |
| Area, THW | 0.2223 in² |
Voltage drop over distance
Single-phase 240 V, carrying 150 A on 1/0 AWG copper.
| One-way distance | Drop | Within 3%? |
|---|---|---|
| 25 ft | 0.38% | Yes |
| 50 ft | 0.76% | Yes |
| 100 ft | 1.53% | Yes |
| 150 ft | 2.29% | Yes |
| 200 ft | 3.05% | No |
| 300 ft | 4.58% | No |
Source: NFPA 70, National Electrical Code, Table 310.16; NFPA 70, National Electrical Code, Table 310.15(B)(1)(1); NFPA 70, National Electrical Code, Table 310.15(C)(1); NFPA 70, National Electrical Code, Chapter 9, Table 8. Published by NFPA.NEC 2023
Related