Volts × amps · Single and three-phase · Free

EV Charger kW Calculator

EV chargers are rated in volts and amps, but what you really want to know is the power in kilowatts and how many miles that adds per hour. This calculator converts a charger’s specs into kW, checks it against your car’s onboard charger limit, and shows the circuit size it needs.

Single and three-phaseOnboard charger limit includedNothing stored

Charger power output

7.68 kW

240 V × 32 A, single-phase

Power your car accepts

7.68 kW

Miles added per hour

27 mi

Charger level

Level 2

Energy in 8 hours

61.4 kWh

Adjust voltage, current, and phase to see your charger’s real output.

The Formula

How Charger Power Is Calculated

Power in kW is voltage times current, divided by 1,000. Three-phase power adds a factor of 1.732, the square root of 3, because the three phases are offset from each other.

Circuit	Formula	Example
Single-phase AC	kW = V × A ÷ 1,000	240 V × 32 A = 7.68 kW
Three-phase AC	kW = 1.732 × V × A ÷ 1,000	208 V × 32 A × 1.732 = 11.53 kW
DC (fast charger output)	kW = V × A ÷ 1,000	400 V × 125 A = 50 kW

This calculator assumes a power factor of 1.0, which is close enough for EV chargers when planning. It uses line-to-line voltage for three-phase circuits.

Reference Table

Common Charger Setups

Where common chargers land on the power scale. Continuous EV charging is limited to 80% of the circuit’s breaker rating, so each charger needs a larger circuit than its own current.

Charger	Voltage	Current	Circuit	Power
Level 1, standard outlet	120 V	12 A	15 A	1.44 kW
Level 1, 20 A outlet	120 V	16 A	20 A	1.92 kW
Level 2, common home setup	240 V	32 A	40 A	7.68 kW
Level 2, 40 A	240 V	40 A	50 A	9.6 kW
Level 2, 48 A hardwired	240 V	48 A	60 A	11.52 kW
Level 2, maximum	240 V	80 A	100 A	19.2 kW
DC fast, lower power	400 V DC	125 A	Commercial	50 kW
DC fast, high power	400 to 800 V DC	up to 500 A	Commercial	150 to 350 kW

Now see how long a charge takes

Power is half the picture. See how long your battery takes to fill, and what it costs.

Charge Time Calculator →Charging Cost

Common Questions

EV Charger kW Questions, Answered

kW measures power, how fast energy flows at any moment. kWh measures energy, the total amount delivered over time. A 7.68 kW charger running for one hour delivers 7.68 kWh, and for five hours delivers 38.4 kWh.

On AC charging, the slowest part of the chain sets the speed: the charger, the circuit, or your car’s onboard charger. A car with a 7.2 kW onboard charger will only draw about 7.2 kW, even from a 19.2 kW charger. That’s why this calculator asks for your car’s onboard limit.

Because EV charging is a continuous load, the charger’s current should be no more than 80% of the breaker rating. A 32 A charger needs a 40 A circuit, a 40 A charger needs 50 A, and a 48 A charger needs 60 A. Have a licensed electrician confirm your panel has the capacity.

Rarely in North America, where homes almost always have single-phase service. Three-phase power is common at commercial sites, where it often feeds DC fast chargers or banks of Level 2 chargers. North American EVs charge from single-phase AC, so three-phase kW here describes site supply, not what one car draws on AC.

Only up to your car’s limit. On AC, your onboard charger caps the speed. On DC fast chargers, the battery’s charging curve caps it, and power drops as the battery fills. Past those limits, a bigger charger adds nothing.

Reference: Standard single-phase and three-phase power formulas; the 80% continuous-load rule for EV charging circuits; EPA ratings via fueleconomy.gov for EV efficiency; typical charger nameplate ratings.

This calculator gives planning estimates using standard electrical formulas. It doesn’t account for power factor, voltage drop, or local code requirements. For circuit design, permits, or installation, use a licensed electrician. EVRatio does not provide electrical engineering advice.