What Size Breaker Do I Need?

The NEC minimum for a freestanding electric range or stove up to 12 kW is a 40A / 240V breaker with #8 copper: NEC Table 220.55 gives an 8 kW demand (about 33A) and NEC 210.19(A)(3) sets a 40A floor for ranges 8.75 kW and larger. In practice most ranges are installed on a 50A / 240V circuit with #6 copper and a NEMA 14-50 receptacle, which is also compliant and gives headroom. A range over 12 kW is sized up to its nameplate, and a gas stove needs only a 120V receptacle for its controls.

A standard 40-50 gallon, 4500W residential water heater is installed on a 30A / 240V breaker with #10 copper. It draws 18.75A, and NEC 422.13 treats a fixed water heater as a continuous load, so it is sized at 125% (23.4A); the code minimum is a 25A breaker, but 30A on #10 is the common install. A 5500W heater is also 30A. Tankless electric units are much larger and need 60-150A total.

An electric dryer uses a 30A / 240V breaker with #10 copper, per NEC 220.54. A gas dryer only needs a standard 120V 15A or 20A circuit for its motor and controls. Under the 2023 NEC, a dryer receptacle now requires GFCI protection, though adoption of that rule varies by jurisdiction.

A 48A EV charger needs a 60A breaker with #6 copper (75°C) wire. EV charging is a continuous load, so NEC 625.42 requires the circuit to be sized at 125% of the charger output: 48A x 1.25 = 60A. A 40A charger uses a 50A breaker, and a 32A charger uses a 40A breaker.

Divide watts by volts to get the running current, then choose the next standard breaker size (NEC 240.6) at or above it. For a continuous load (on 3 hours or more, such as a water heater, EV charger, or baseboard heat), size the breaker at 125% of that current first (NEC 210.20(A)). Example: a 3000W, 240V load draws 12.5A, so the minimum breaker is 15A (or 20A if continuous). Always size the wire to the breaker and confirm against the nameplate.

Yes. The conductor must be able to carry the breaker's rating: 14 AWG copper for 15A, 12 AWG for 20A, 10 AWG for 30A, 8 AWG for 40A, and 6 AWG for 50A (and for 60A with 75°C wire). The NEC 240.4(D) small-conductor rule caps 14, 12, and 10 AWG copper at 15, 20, and 30A regardless of their higher table ampacity. Putting a larger breaker on undersized wire is the most dangerous wiring mistake because the breaker will not trip before the wire overheats.

Motor loads follow NEC Article 430, not a flat rule. You size them from the table full-load current (NEC 430.248), not the nameplate: the conductor is 125% of FLC and the breaker can be up to 250% of FLC so the motor can start, which is why a motor circuit shows a small wire under a larger breaker. See the motor full-load current chart for the exact sizes by horsepower.

Air conditioners and heat pumps are sized from the nameplate Minimum Circuit Ampacity (MCA) and Maximum Overcurrent Protection (MOCP) under NEC Article 440, not a flat rule. Use the MOCP printed on the unit as the maximum breaker and the MCA to size the wire. A typical 2-3 ton condenser lands on a 30A breaker, but always read the nameplate.