What size wire for 150 amps?
1/0 AWG copper — at 75 °C terminals, NEC Table 310.16. Aluminum: 3/0 AWG.
A 150 A circuit needs 1/0 AWG copper, rated 150 A at 75 °C. At this size the conductors are single conductors in conduit or SER cable; NM-B is not manufactured heavy enough to apply.
Safety first. This is a starting point before derating, not a load calculation. Wire sizing affects fire and shock safety — verify against the current NEC and have circuits designed or reviewed by a licensed electrician for your jurisdiction.
150 amp wire size by material and terminal rating
| Material | 60 °C (NM-B) | 75 °C (typical) | 90 °C |
|---|---|---|---|
| copper | 3/0 AWG (165 A) | 1/0 AWG (150 A) | 1/0 AWG (170 A) |
| aluminum | 4/0 AWG (150 A) | 3/0 AWG (155 A) | 2/0 AWG (150 A) |
Sizes are the smallest conductor whose ampacity and NEC 240.4(D) breaker cap both reach 150 A, before any derating. Use the 75 °C column unless every terminal, breaker and device in the circuit is rated otherwise (NEC 110.14(C)).
If the load runs continuously
A load operating for three hours or more is a continuous load, and NEC 210.19(A)(1) requires the conductor to be sized at 125% of it — 150 A becomes 187.5 A for sizing purposes. That moves this circuit to 3/0 AWG copper , one or more sizes above the 1/0 AWG the plain table suggests. EV chargers, electric heat and commercial lighting are the loads this catches most often.
How far can a 150 amp circuit run?
The table above only prevents overheating. On a long run the limit is voltage arriving at the far end, and it bites well before ampacity does. These are the longest one-way runs for 1/0 AWG copper at 150 A within the 3% drop recommended by the NEC 210.19(A) informational note — and what going up to 2/0 AWG buys you.
| System | Typical use | 1/0 AWG | 2/0 AWG |
|---|---|---|---|
| 120 V | standard receptacle and lighting circuits | 122 ft | 154 ft |
| 240 V | ranges, dryers, EV chargers, feeders | 244 ft | 308 ft |
| 12 V DC | automotive, marine, solar and battery runs | 12 ft | 15 ft |
Single-phase, one-way distance, copper at 20 °C. Aluminum reaches its limit at roughly 60% of these distances. The 3% target is a recommendation, not a code requirement.
What runs on a 150 amp circuit
- dwelling services
- large subpanels
- shop and barn feeders
The catch at 150 amps
150 A is 1/0 copper or 3/0 aluminum under Table 310.16 — but a dwelling service under 310.12 can drop to 1 AWG copper / 1/0 aluminum. That is a two-size difference in aluminum for the same 150 A, and confusing the two tables is the most common feeder-sizing error at this size.
Working the other way round? See how many amps 1/0 AWG carries , including its diameter, resistance and full run-length table.