NEC Wire Sizing
What Size Wire for Each Appliance?
The breaker and wire for the appliances people wire most often, at a glance, each computed from the NEC tables. Pick an appliance for the full detail, code basis, and calculator.
| Appliance | Volts | Breaker | Copper Wire | Ground |
|---|---|---|---|---|
| Electric Dryer | 240V | 30A | #10 | #10 |
| Electric Range | 240V | 50A | #6 | #10 |
| Electric Wall Oven | 240V | 40A | #8 | #10 |
| Electric Cooktop | 240V | 40A | #8 | #10 |
| Electric Water Heater | 240V | 30A | #10 | #10 |
| Hot Tub (GFCI) | 240V | 50A | #6 | #10 |
| Dishwasher (GFCI) | 120V | 20A | #12 | #12 |
| Garbage Disposal | 120V | 15A | #14 | #14 |
| Built-In Microwave | 120V | 20A | #12 | #12 |
Values are the standard circuit for a typical unit. Motor-driven appliances (well pumps, air compressors) and nameplate-MCA loads (mini splits, central AC) follow NEC Articles 430 and 440 and are sized to their data plate.
Pick an Appliance
Electric Dryer
#10 copper on a 30A / 240V circuit.
Electric Range
#6 copper on a 50A / 240V circuit.
Electric Wall Oven
#8 copper on a 40A / 240V circuit.
Electric Cooktop
#8 copper on a 40A / 240V circuit.
Electric Water Heater
#10 copper on a 30A / 240V circuit.
Hot Tub
#6 copper on a 50A / 240V circuit, GFCI.
Dishwasher
#12 copper on a 20A / 120V circuit, GFCI.
Garbage Disposal
#14 copper on a 15A / 120V circuit.
Built-In Microwave
#12 copper on a 20A / 120V circuit.
Central Air Conditioner
Sized to the nameplate MCA and MOCP (NEC 440), not the tonnage. Typical 2-3 ton = #10 Cu.
Mini Split
Inverter ductless unit: size to the nameplate MCA. Typical 12k BTU = #14 Cu on 15-20A.
Tankless Water Heater
Large multi-circuit load: an 18 kW unit draws ~75A across 2-3 circuits of #8 Cu.
Wire Size Calculator
Size any load, distance, and conditions per NEC 310.16 with derating.
EV Charger Wiring
Wire, breaker, and panel for a Level 2 EV charger install.
Frequently Asked Questions
How do I know what size wire an appliance needs?
Start with the appliance nameplate, which lists the minimum circuit ampacity and the maximum breaker. Size the breaker to that (rounded to a standard size), then match the conductor to the breaker at the NEC Table 310.16 column for your terminals: 60C for NM-B cable and terminations 100A and under, 75C for THHN in conduit on 75C-rated lugs. The table on this page gives the typical answer for common appliances, but the nameplate always governs.
Why does an electric water heater use a bigger circuit than its amp draw?
Because NEC 422.13 treats a fixed storage water heater as a continuous load, so the circuit is sized at 125% of the draw. A 4500W / 240V heater pulls 18.75A, and 18.75 x 1.25 = 23.4A, which rounds up to a 30A circuit with #10 copper.
Do 240V appliances need a neutral?
It depends on the appliance. A pure 240V load (like a water heater or baseboard heater) needs only two hots and a ground. Appliances with 120V controls or accessories (modern electric ranges and dryers) need two hots, a neutral, and a ground, which is why they use a 4-wire cord and receptacle (NEMA 14-30 for dryers, 14-50 for ranges) rather than the old 3-wire style.