Breaker GuideNEC 2023 · 2026 · Updated Apr 2026

15 Amp Breaker: Wire Size and Uses

A 15A breaker requires minimum 14 AWG copper or 12 AWG aluminum at 120V. Maximum continuous load: 12A (80% rule). Standard size per NEC 240.6(A).
Copper14 AWG
Aluminum12 AWG
Voltage120V
Max continuous12A

Common uses for a 15A breaker

Lighting, general-purpose outlets, bedroom circuits. Most basic residential circuit. 14 AWG copper is the minimum per NEC 240.4(D).

The 15A breaker is the baseline residential circuit. It powers most rooms where heavy appliances are not present. Pairing it with 14 AWG copper is the minimum allowed per NEC 240.4(D)(3) - you cannot use 14 AWG on a 20A breaker. For kitchens, bathrooms, garages, and outdoor areas, the NEC requires 20A circuits instead.

Wire size for a 15A breaker

The wire must have an ampacity that meets or exceeds the breaker rating at the appropriate temperature column. Here are the minimum wire sizes:

MaterialMinimum wireDetails
Copper14 AWGStandard for residential branch circuits
Aluminum12 AWGCommon for feeders and above and larger

These sizes assume 75°C termination temperature per NEC 110.14(C), which is the standard for most residential breakers and devices. For long wire runs, check voltage drop - you may need to upsize the wire even though the ampacity is adequate.

Continuous load rule (80% maximum)

For continuous loads - any load expected to run for 3 hours or more - the NEC requires that the load not exceed 80% of the breaker rating (NEC 210.20(A)). On a 15A breaker, the maximum continuous load is 12A.

This is why sizing often seems counterintuitive:

Installation notes

Breaker type: A 15A breaker is a single-pole (120V) breaker. It occupies one slot in the panel. The breaker connects one hot conductor to one bus bar in the panel, providing 120V to neutral.

Ground wire: A 15A circuit requires a minimum 14 AWG copper equipment grounding conductor per NEC Table 250.122.

Standard sizes: 15A is a standard breaker size per NEC 240.6(A). Standard residential breaker sizes are: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200. Non-standard sizes should never be used.

Why does my 15A breaker keep tripping?

A 15A breaker trips when the combined load on the circuit exceeds 15 amps, which happens more often than people expect. The usual culprit: a space heater (12.5A) on the same circuit as a lamp and a phone charger. Space heaters are the single most common cause of 15A breaker trips in residential wiring. The fix is either a dedicated circuit for the heater or moving it to a 20A circuit that can handle the load. If the breaker trips with no obvious overload, check for a ground fault - a damaged cord behind furniture or a nail through a cable in the wall.

Frequently asked questions

What wire size for a 15 amp breaker?

14 AWG copper or 12 AWG aluminum minimum. The wire must have an ampacity at the 75°C column that meets or exceeds 15A. For long runs, you may need to upsize for voltage drop.

What can a 15 amp breaker handle?

Lighting, general-purpose outlets, bedroom circuits. For continuous loads (3+ hours), the maximum is 12A (80% of 15A). For non-continuous loads, the full 15A is available.

Can I put a 15A breaker on 12 AWG wire?

The breaker must not exceed the wire ampacity. 14 AWG copper supports a 15A breaker. Never put a larger breaker on wire that cannot handle it - this defeats the safety purpose of the breaker.

Is 15A a standard breaker size?

Yes. 15A is a standard breaker size per NEC 240.6(A). It is widely available from all major breaker manufacturers (Square D, Eaton, Siemens, GE). Always use the correct breaker brand for your panel - breakers are not interchangeable between panel brands.

What to buy

🔌14 AWG WireCopper THHN for 15A circuitCheck prices on Amazon (paid link)⚡15A BreakerStandard overcurrent protectionCheck prices on Amazon (paid link)

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NEC 2023 references verified April 2026