Home Charger Amp & Breaker Calculator
Estimate the continuous amp draw and minimum breaker rating for a U.S. home Level 2 EV charger. A planning estimate only; wire sizing needs an electrician.
Free calculator, no signup required. Runs in your browser — your entries stay on this device (saved in this browser until you clear them) and are not sent to us.
What this estimates, and what it does not
This is a U.S. planning estimate for a single-phase continuous charging load at 120 V, 208 V or 240 V. It uses the common 80% rule: the continuous current should not exceed 80% of the breaker rating, so the breaker must be at least 125% of that current. It then rounds up to the next size in a short list of common breaker ratings (15 to 100 A). Other regions and voltages, such as 230 V systems, are not covered.
Worked example (illustrative assumptions)
Assumptions: a 7.4 kW charger on a 240 V circuit. 7,400 ÷ 240 = 30.8 A continuous. 30.8 ÷ 0.8 = 38.5 A minimum, so the next common size in the list is 40 A.
Outside the supported range
If the minimum breaker rating is above 100 A, the tool says the load is outside its supported range instead of showing a breaker size. For example, 100 kW at 240 V needs about 521 A, so it is not estimated.
What it does not decide
It does not size conductors, check voltage drop, panel capacity, ground-fault protection, permits or local code, and it gives no wire size. Those depend on your installation and must be worked out by a licensed electrician.
This is a planning estimate, not an installation guide. Have any charger circuit designed and installed (or at least inspected) by a licensed electrician under your local code.
Frequently asked
Why is the breaker rated higher than the charger's actual amp draw?
This estimator applies the common U.S. planning rule that a continuous load should use no more than 80% of the breaker rating, which is the same as a breaker of at least 125% of the load. A 32 A continuous load works out to a minimum of 40 A. Your local code and electrician decide what actually applies to your installation.
What is the difference between 16, 32, 40, and 48 A chargers?
At 240 V the continuous current sets the power: 16 A is about 3.8 kW, 32 A about 7.7 kW, 40 A about 9.6 kW and 48 A about 11.5 kW. Using the 80% planning rule, the minimum breaker ratings work out to 20 A, 40 A, 50 A and 60 A. Higher power charges faster; the Charging Time Calculator shows how much.
Do I need a licensed electrician to install a Level 2 charger?
Installing or modifying a circuit for a charger is electrical work that generally needs a qualified electrician and, in many places, a permit and inspection. Requirements vary by location, so ask your local authority or electrician. This calculator cannot tell you what your location requires.
Can I plug a Level 2 charger into an existing dryer outlet?
Whether an existing outlet is suitable depends on the outlet, the circuit and the charger, and this estimator cannot tell you. Do not assume it is safe. Have a licensed electrician inspect the existing circuit before you use it for continuous EV charging.
What wire size do I need?
This estimator does not give a wire size. Conductor selection depends on the conductor material, run length, temperature rating, installation method, voltage drop and local code, none of which this tool knows. A licensed electrician must size the conductors for your installation.