150 amp wire size
A 150 amp feeder sized at its full rating needs 1/0 AWG copper or 3/0 AWG aluminum in the 75 °C column. As a dwelling service or main feeder under NEC 310.12, sized at 83% of 150 A, the minimum drops to 1 AWG copper or 2/0 AWG aluminum.
Minimum wire size for 150 A
| Conductor | 60 °C column | 75 °C column |
|---|---|---|
| Copper | Not listed | 1/0 AWG |
| Aluminum | Not listed | 3/0 AWG |
| Dwelling service, 83% (124.5 A) | — | 1 AWG Cu · 2/0 AWG Al |
Usually chosen: 2/0 AWG aluminum or 1 AWG copper for a 150 A dwelling service; 3/0 AWG aluminum or 1/0 AWG copper for a 150 A subpanel feeder.
Breaker rating taken as the required ampacity; 240.4(D) limits applied. The charts list no 60 °C aluminum, and 60 °C copper only to 2 AWG (95 A), the largest NM-B. Manufacturer chart values (2017 NEC basis). Verify against the NEC edition adopted locally.
150 A sits between the old 100 A service and today's common 200 A one. It is a frequent size for service upgrades on smaller houses and for large subpanels; the sections below cover which sizing rule applies and when a long run needs more copper or aluminum.
Where 150 amp circuits are used
Many service upgrades from 100 A stop at 150 A, which is enough for a moderate house with gas heat or a heat pump and fits meter bases and panels that are cheaper than 200 A equipment. All-electric houses more often need 200 A.
A 150 A feeder serves large subpanels: a detached garage with a lift, welder and EV charger, a pole barn workshop, or a second panel in a big house. A main panel rated 200 A or 225 A often has a 150 A feeder breaker for a downstream panel.
Dwelling services and main feeders: the 83% rule
Under NEC 310.12, service and feeder conductors rated 100 A through 400 A that supply the whole load of a one-family dwelling, or of one dwelling unit in a two-family or multifamily building, may be sized at 83% of the rating. For 150 A that is 124.5 A (wording verified against the 2020 edition of the code).
In the 75 °C column, 1 AWG copper at 130 A and 2/0 AWG aluminum at 135 A meet 124.5 A; 1/0 aluminum, at 120 A, does not. Correction for high ambient temperature and adjustment for bundling still apply, and the reduced size is permitted only where the conductors carry the full dwelling load.
Voltage drop at 150 A
1/0 AWG copper at the full 150 A stays within 3% to about 197 ft at 240 V. A feeder to an outbuilding at the back of a large lot can exceed that, and the table shows when 2/0, 3/0 or larger copper is needed.
Aluminum of the next size or two up has about the same resistance as the copper sizes in the table: 3/0 aluminum is close to 1/0 copper, which is why the two are treated as equivalents for 150 A feeders.
| One-way length (ft) | Drop at 120 V (%) | Drop at 240 V (%) | Copper for 3% at 120 V | Copper for 3% at 240 V |
|---|---|---|---|---|
| 25 | 0.76 | 0.38 | 1/0 AWG | 1/0 AWG |
| 50 | 1.52 | 0.76 | 1/0 AWG | 1/0 AWG |
| 75 | 2.28 | 1.14 | 1/0 AWG | 1/0 AWG |
| 100 | 3.05 | 1.52 | 2/0 AWG | 1/0 AWG |
| 150 | 4.57 | 2.28 | 3/0 AWG | 1/0 AWG |
| 200 | 6.09 | 3.05 | 250 kcmil | 2/0 AWG |
| 250 | 7.61 | 3.81 | 300 kcmil | 3/0 AWG |
| 300 | 9.14 | 4.57 | 350 kcmil | 3/0 AWG |
Full rating on a single-phase circuit, copper at 75 °C, stranded.
Breaker pairing
A two-pole 150 A breaker protects the feeder, or a 150 A main breaker the service. 1 AWG copper (130 A) and 2/0 aluminum (135 A) may also be used on a 150 A subpanel feeder under the next-size-up rule of 240.4(B), because neither ampacity is a standard rating, provided the calculated load does not exceed the conductor's ampacity.
That allowance is a common way to keep a 150 A feeder at 2/0 aluminum where the load calculation is modest; the 83% rule is a separate path that applies only to the main dwelling service or feeder.
NM-B cable or THHN in conduit
NM-B is not made in these sizes. 150 A feeders are run as SER or SEU cable, as THHN/THWN-2 or XHHW-2 in conduit, or as direct-buried USE-2 and URD for laterals and long underground runs.
SER cable used inside a house is installed under the rules for NM cable, and where it is buried in thermal insulation it falls to the 60 °C column, which can push the size up.
Copper or aluminum
Aluminum is the usual choice at 150 A: 2/0 aluminum for a dwelling service and 3/0 aluminum for a full-rating feeder, against 1 AWG and 1/0 copper. The cost difference per foot is large, and modern AA-8000 conductors with properly torqued AL/CU lugs have a good service record.
Copper remains common in conduit runs where pulling space is tight, since 1/0 copper is smaller in diameter than 3/0 aluminum.
Common mistakes
Sizing a 150 A garage feeder at 83%
The 83% rule covers only conductors carrying the whole dwelling load. A 150 A feeder to a garage subpanel is sized at 150 A, or by 240.4(B) with a load calculation.
Choosing 1/0 aluminum for a 150 A service
1/0 aluminum is rated 120 A at 75 °C, below the 124.5 A that 83% of 150 A requires. The dwelling service minimum in aluminum is 2/0.
Undersizing the equipment ground
A 150 A feeder needs a 6 AWG copper or 4 AWG aluminum equipment grounding conductor under Table 250.122, larger if the phase conductors are upsized for voltage drop.
Mixing conductor materials on one lug
Copper and aluminum conductors may not share a terminal unless it is listed for that combination. Each lug's marking states which conductors and how many it accepts.
Frequently asked questions
What size wire is needed for a 150 amp service?
For a dwelling service under NEC 310.12, the minimum is 1 AWG copper or 2/0 AWG aluminum, sized at 83% of 150 A. Outside that rule, 1/0 copper or 3/0 aluminum is required.
What size wire is needed for a 150 amp subpanel?
1/0 AWG copper or 3/0 AWG aluminum at the 75 °C column. Where the calculated load is lower, 240.4(B) may permit 1 AWG copper or 2/0 aluminum on the 150 A breaker.
Can 2/0 aluminum be used for 150 amps?
Yes, as a dwelling service or main feeder under the 83% rule, or on a 150 A breaker under the next-size-up rule when the load does not exceed 135 A.
Is 1/0 copper good for 150 amps?
Yes. 1/0 AWG copper is rated 150 A in the 75 °C column, so it suits any 150 A feeder with 75 °C terminations, whether or not the 83% rule applies.
Is a 150 amp service enough for a house?
That depends on the dwelling load calculation of NEC Article 220, which counts the floor area, appliances, heating and cooling and any EV charging. Many houses with gas heat fit within 150 A; all-electric houses often need 200 A.