EV Charger Amps Calculator
Level 2 charging current depends mostly on charger power and supply voltage; breaker sizing then follows the continuous-load 125% rule
Use this EV-specific calculator when you want charging amps and the minimum branch-circuit size in one step. The math is the same idea as kW to amps, but this version keeps the focus on 208V and 240V Level 2 charging and applies the continuous-load rule automatically. After you know the breaker size, confirm the conductor with the wire size calculator.
Estimated charging current: 30 A
Minimum breaker: 40A double-pole
Some shorter-run setups may start around 8 AWG copper, but confirm final conductor size with the wire size calculator, EVSE instructions, and local code.
How to size an EV charger circuit from charging power
Level 2 charging is usually described by power, like 7.2 kW, 9.6 kW, or 11.5 kW. To plan the circuit, you need to convert that power into current. Lower voltage means more current for the same charging power, which is why a charger on 208V can draw more amps than you might expect from a 240V rule of thumb.
EV charging is treated as a continuous load because charging sessions often last well beyond three hours. That means the branch circuit has to be sized at 125% of the charger current. A charger drawing 32A does not go on a 32A breaker. It normally needs at least a 40A breaker.
This calculator is most useful when you know the charger output or the model's advertised kW rating and want to sanity-check whether you are really looking at a 40A, 50A, or 60A circuit before you price wire, a new breaker, or a panel upgrade.
- Charger output in kilowatts
- Supply voltage: 208V or 240V
- Continuous-load sizing at 125%
- Common breaker sizes available above the calculated requirement
Do not size the breaker to the charger amps alone. Size the circuit to 125% of the charging current.
How to convert
Step 1: Convert charging power to current
Charging amps come from the charger power and the supply voltage.
Charging amps = (kW x 1000) / volts
Step 2: Apply the continuous-load rule
Level 2 charging is typically sized as a continuous load.
Minimum circuit amps = charging amps x 1.25
Step 3: Round up to a common breaker size
Once you have the required circuit current, round up to the next common breaker size.
Common sizes: 20A, 30A, 40A, 50A, 60A, 70A, 80A, 100A
Worked examples
Question: What does a 7.2 kW charger draw at 240V?
Solution: Charging amps = 7.2 x 1000 / 240 = 30A. Minimum circuit = 30 x 1.25 = 37.5A. Round up to 40A.
Question: What does a 9.6 kW charger draw at 240V?
Solution: Charging amps = 9.6 x 1000 / 240 = 40A. Minimum circuit = 40 x 1.25 = 50A. Round up to 50A.
Question: What does a 6.6 kW charger draw at 208V?
Solution: Charging amps = 6.6 x 1000 / 208 = 31.73A. Minimum circuit = 31.73 x 1.25 = 39.66A. Round up to 40A.
Common mistakes and notes
- 240V is common in homes, while 208V often shows up in condos, apartments, and commercial parking garages.
- The charger label may list output current directly. If it does, that value is often the better starting point than back-calculating from kW.
- After you know the breaker size, check wire size separately because run length can still change the conductor choice.
- Panel capacity matters too. A 40A or 50A EV circuit can be too much for some already-busy 100A services.
Assumptions
- Level 2 AC EV charging estimate at 208V or 240V.
- Assumes the charger is a continuous load and applies the 125% sizing rule to the branch circuit.
- Rounds up to common residential and light-commercial breaker sizes for planning.
- Final conductor size still depends on breaker size, conductor material, terminal temperature rating, installation conditions, run length or voltage drop, and the EVSE instructions plus local code.
- Actual installation rules still depend on the EVSE instructions, panel capacity, conductor type, and local code.
Worked example
Example: A 9.6 kW charger at 240V draws 40A, and the continuous-load rule points to a 50A breaker.
FAQ
Why does the breaker size come out larger than the charger amps?
Because EV charging is usually treated as a continuous load. Continuous loads are sized at 125% of the running current, which is the same idea as keeping a breaker at 80% or less for long sessions.
What is the difference between 208V and 240V charging?
A 208V charger needs more current to deliver the same kilowatt output because the voltage is lower. That can change charging speed expectations and sometimes the circuit size, especially when you are close to a breaker-size boundary.
Can I use this calculator for a plug-in portable charger?
Yes for a rough planning check, but portable chargers are limited by the receptacle and branch circuit they plug into. Always follow the charger manufacturer's instructions and the receptacle rating.
Does this calculator tell me whether my panel can handle the charger?
No. It tells you charger current and a minimum branch-circuit size. Main service capacity is a separate question that depends on the full household load and the service rating.
What is a common home Level 2 charger size?
Many common home chargers land around 7.2 kW to 9.6 kW, which usually means 30A to 40A charging current and a 40A to 50A branch circuit. Higher-output models can push into 48A charging with a 60A circuit.
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⚠️ Sanity Check Only
This tool provides informational estimates only. It is not professional engineering advice. Electrical work is dangerous and governed by strict local codes.
Before you start:
- Verify these results with a licensed electrician.
- Cross-reference with the latest Electrical Code (NEC/CEC).
- Never work on live circuits.