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What Size Breaker for 1/0 AWG Wire?

For 1/0 AWG wire under the displayed non-receptacle defaults, the largest common breaker is 150 A for copper and 125 A for aluminum. The aluminum result is a next-size-up breaker-protection limit from 120 A usable ampacity, not a full 125 A load rating.
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Breaker Starting Point

Maximum common breaker sizes under common conditions. Derating or receptacle limits can reduce these.

MaterialConductorLargest common breakerAssumptions
Copper1/0 AWG copper150 A90 C insulation, 75 C lugs, 86 F, 3 current-carrying conductors, non-receptacle circuit default
Aluminum1/0 AWG aluminum125 A90 C insulation, 75 C lugs, 86 F, 3 current-carrying conductors, non-receptacle circuit default
What Size Breaker for 1/0 AWG Wire? under common non-receptacle defaults: 90 C insulation, 75 C lugs, 86 F ambient, no more than three current-carrying conductors, and next-size-up checks only where eligible.

What 1/0 AWG ChangesAt 1/0 AWG, copper is a clean 150 A feeder-protection result under the displayed defaults, while aluminum reaches 125 A only through next-size-up. Treat this as a feeder compatibility check, not a shortcut around load calculation, terminal temperature, raceway, and equipment listings.

Check breaker and wire together

Adjacent Wire Sizes

See whether stepping one conductor size changes the maximum standard breaker.

WireCopper max breakerAluminum max breaker
1 AWG150 A100 A
1/0 AWG (this page)150 A125 A
2/0 AWG175 A150 A
Largest common breakers for 1/0 AWG and neighboring published wire sizes under the same defaults.

1/0 AWG Is the First Ought-Size Feeder Step

Large feeder context for 1/0 AWG wire.

A 1/0 AWG breaker-size search usually comes from a larger feeder, service-adjacent equipment, or a comparison after 1 AWG no longer fits the plan.

Under the displayed defaults, 1/0 AWG copper lands on a 150 A maximum breaker. 1/0 AWG aluminum reaches 125 A through the non-receptacle next-size-up path from 120 A usable ampacity, so the material choice changes both the breaker and the load-sizing question.

Field Checks for This Wire Size

Checks that matter in this conductor band — not a generic breaker list.

  • Keep copper at 150 A

    The 150 A maximum belongs to 1/0 AWG copper under these defaults. Do not transfer that result to 1/0 AWG aluminum.

  • Name the aluminum next-size-up step

    The 125 A aluminum maximum comes from 120 A usable ampacity through the non-receptacle next-size-up default. It is not a 125 A load rating.

  • Check continuous and actual load

    A continuous or full-rated feeder load can require more conductor ampacity than the breaker-protection maximum suggests. Run the load calculation before using this result.

  • Confirm lug range and 60 C limits

    Equipment lugs must accept 1/0 AWG in the chosen material, and 60 C terminations can reduce the usable ampacity before the breaker is selected.

1/0 AWG Breaker FAQs

What size breaker for 1/0 AWG wire?
Under the displayed non-receptacle defaults on this page, 1/0 AWG copper has a 150 A maximum breaker and 1/0 AWG aluminum has a 125 A maximum breaker.
Can 1/0 AWG aluminum use a 150 A breaker?
No under these defaults. The 150 A result belongs to copper. The 1/0 AWG aluminum row returns a 125 A maximum breaker, and that value depends on next-size-up eligibility.
Is the 125 A aluminum result a 125 A load rating?
No. It is a breaker-protection result from 120 A usable ampacity under the non-receptacle next-size-up default. A full 125 A feeder load can require a larger conductor.
Can I use this page as final approval for a 1/0 AWG feeder?
No. Treat it as a compatibility starting point only. Feeder work still needs load calculation, terminal temperature, conductor material, raceway fill, voltage drop, equipment listings, and AHJ review.