Home energy · EV charging

What breaker does a charger need?

Charger amps and volts in, kW and minimum circuit protection out. A planning aid for the conversation with your electrician, not an installation design.

Inputs

Starting values are illustrative, not current prices or specifications. Replace each with your own.

Result

Answer

A charger rated at 32 A on 240 V delivers 7.68 kW and needs circuit protection of at least 32 × 1.25 = 40 A, because EV charging counts as a continuous load. Wire size, panel capacity and local code still decide what can be installed.

Worked example

A 32 A charger on 240 V is 32 × 240 ÷ 1,000 = 7.68 kW. The circuit protection must be at least 32 × 1.25 = 40 A, so a 40 A breaker is the smallest common size. A 48 A charger needs 60 A at minimum (11.52 kW). A 30 A charger (7.2 kW) needs 37.5 A, so the next size is 40 A, which matches the dedicated 40 A circuit AFDC describes for 7.2 kW home units.

Formulas and notes

kW = amps × volts ÷ 1,000.
Minimum circuit protection = charger amps × 1.25 (EV charging is a continuous load per EC&M, NEC 625.42; continuous loads are conventionally sized at 125%, a rule of thumb the AFDC 30 A to 40 A example agrees with).
Next size = the smallest value in 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 125, 150 A that is at least the minimum.
Largest continuous charger on a breaker = breaker amps ÷ 1.25.
Not modelled: wire gauge, voltage drop, panel or service capacity, load management, local amendments, and the Canadian Electrical Code differences. These decide the real answer.

Electrical safety: this page is not electrical advice. Charger circuits must be designed and installed by a licensed electrician to your local code. Do not use extension cords or adapters for sustained EV charging.

Planning estimate only, not professional advice. Sources, checked 2026-10-08: EC&M, NEC Requirements for EV Equipment (Nov. 9, 2023) · U.S. DOE Alternative Fuels Data Center, Electric Vehicle Charging Stations

FAQ

What size breaker do I need for a 48 amp EV charger?

At least 60 A. EV charging is a continuous load (EC&M, NEC 625.42), and continuous loads are conventionally sized at 125 percent of the load: 48 × 1.25 = 60 A. The AFDC 30 A to 40 A example is consistent with this.

Why is the breaker bigger than the charger amps?

Because the charger runs for hours at a steady load, protection and conductors are sized with a 25 percent margin so the circuit does not run at its limit for the whole charge.

Can I install an EV charger circuit myself?

Have a licensed electrician do the work and pull any permit your jurisdiction requires. This calculator is a planning aid and does not select wire, check your panel or know your local code.

How many kW is a 40 amp EV charger?

On 240 V, 40 A is 9.6 kW. Its circuit protection would need to be at least 50 A.

Does this apply in Canada?

The 125 percent continuous-load convention used here follows U.S. National Electrical Code practice. Canada uses the Canadian Electrical Code and provincial rules, which can differ, so confirm with a licensed Canadian electrician.