150 amp wire size

A 150 amp circuit needs 1/0 AWG copper or 3/0 AWG aluminum wire with 75 °C terminations.

150 amp wire size by termination rating

Wire size for a 150 amp circuit by termination temperature rating (60 °C: NM-B cable; 75 °C: THHN and most breakers), with the ground wire
Termination rating	Copper	Aluminum
60 °C	3/0 AWG	4/0 AWG
75 °C, THHN	1/0 AWG	3/0 AWG
Ground wire	6 AWG	4 AWG

150 amp wire size by distance at 240 V

Sizes that keep the voltage drop within 3% on a 240 V circuit loaded to the full 150 A, 75 °C terminations. The copper ground wire grows with the hot wires on long runs.

Wire size for a 150 amp, 240 V circuit by one-way distance, keeping the voltage drop within 3%
One-way distance	Copper	Drop	Copper ground	Aluminum	Drop
25 ft	1/0 AWG	0.4%	6 AWG	3/0 AWG	0.4%
50 ft	1/0 AWG	0.8%	6 AWG	3/0 AWG	0.8%
100 ft	1/0 AWG	1.5%	6 AWG	3/0 AWG	1.6%
150 ft	1/0 AWG	2.3%	6 AWG	3/0 AWG	2.4%
200 ft	2/0 AWG	2.4%	4 AWG	4/0 AWG	2.5%
300 ft	3/0 AWG	2.9%	4 AWG	300 kcmil	2.7%

Copper
Aluminum

Wire size for 150 A at 240 V by distance, within 3% voltage drop.

Check your own 150 amp run

What are you sizing for?

Breaker or load

One-way distance

From the panel to the load, not there and back

Voltage

Conductor

Termination rating

Result

1/0 AWG copper

Ampacity sets the size; the voltage drop is within 3%.

Breaker: 150 A
Voltage drop: 1.8 V (0.8%)
Volts at the load: 238.2 V
Ground wire: 6 AWG copper

How it is calculated

Breaker: 150 A rounded up to a standard size = 150 A.
Smallest copper conductor rated for 150 A at 75 °C: 1/0 AWG.
Drop = 2 × K × 150 A × 50 ft ÷ 105,600 cmil = 1.83 V, target 3% of 240 V.

What a 150 amp circuit is used for

House service
Large sub panel

Sources

NFPA 70, National Electrical Code (2023): Allowable ampacities of insulated conductors, Table 310.16
NFPA 70, National Electrical Code (2023): Overcurrent protection of small conductors, Section 240.4(D)
NFPA 70, National Electrical Code (2023): Conductor properties, Chapter 9 Table 8
NFPA 70, National Electrical Code (2023): Minimum size equipment grounding conductors, Table 250.122

Compared with 9 published documents, last on 2026-11-13

American Wire Group (edition not stated): Allowable Ampacities of Insulated Aluminum or Copper-Clad Aluminum Conductors — Aluminum columns and the 15/25 A aluminum small-conductor limits
Cerrowire (NEC 2017): Ampacity Charts — Copper 60/75/90 °C and aluminum 75/90 °C, 14 AWG to 600 kcmil
LugsDirect (NEC 2020): Ampacities of Insulated Conductors From NEC Table 310.16 — All columns, copper and aluminum, every size on this site
LugsDirect (AWG formula): AWG Wire Chart, kcmil and Metric Wire Sizes — Circular mils, square millimeters and diameters by size
Michigan State University, Biosystems and Agricultural Engineering (NEC edition not stated): Electrical Tech Note 212: Conductor Properties — Conductor area, dc resistance at 75 °C and the K constants
Omni Cable (NEC 2017): NEC Ampacity Data — All columns, copper and aluminum
Southwire (NEC 2023): SPEC 10003, THHN/THWN-2 building wire — 14–10 AWG copper and the 15/20/30 A small-conductor limits
Southwire (NEC 2023): SPEC 45007, aluminum XHHW-2 building wire — Copper small-conductor limits 15/20/30 A
Tucson Electric Power (edition not stated): Service requirements SR-453, grounding conductor tables — Equipment grounding and grounding electrode conductor sizes

Calculated by Calculate.diy with the method of the National Electrical Code® (NEC®), 2023 edition; not the NEC text. Methodology. For planning only: check local code and use a licensed electrician.

150 amp wire size

150 amp wire size by termination rating

150 amp wire size by distance at 240 V

Check your own 150 amp run

What a 150 amp circuit is used for

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