kW ↔ Amps Converter
Convert between kilowatts and amps at any voltage — useful for sizing chargers, wires and breakers.
The relationship — Ohm's law for power
Power (in watts), voltage (in volts) and current (in amps) are tied together by a simple equation:
So amps = watts ÷ volts, and watts = volts × amps. To go to kilowatts (kW), divide watts by 1,000.
Worked example
A 7.4 kW EV charger on a 240 V home circuit pulls 7,400 W ÷ 240 V = 30.8 amps continuously. With the NEC’s 80% rule for continuous loads, it needs a 40 A breaker.
Common EV charger amperages
- 120 V Level 1 — 12 A draw, ~1.4 kW
- 240 V at 16 A — ~3.8 kW (small Level 2)
- 240 V at 32 A — ~7.4 kW (most common Level 2 home charger)
- 240 V at 40 A — ~9.6 kW (faster home charger)
- 240 V at 48 A — ~11.5 kW (Tesla Wall Connector, Wallbox Pulsar Plus high)
Continuous EV charging is a special “continuous load” under the U.S. National Electrical Code — the circuit’s breaker must be sized for 125% of the actual draw, or equivalently the charger can only use 80% of the breaker. A 32 A continuous charger needs a 40 A breaker. For a quick build, the Home Charger Amp Calculator handles the breaker sizing automatically.
Frequently asked
How does the kW-to-amps formula work?
Power equals voltage times current. So watts = volts × amps, and amps = watts ÷ volts. Divide watts by 1,000 to get kilowatts. A 7,400 watt charger on 240 V draws 7,400 ÷ 240 = 30.8 amps.
What is the "80% rule" for EV chargers?
The US National Electrical Code treats EV charging as a continuous load — running 3+ hours at a time. The circuit must be rated for 125% of the actual draw, which means the charger can only use 80% of the breaker. A 32 A continuous load needs a 40 A breaker.
Why does voltage matter so much?
For the same kilowatts, double the voltage means half the current. A 7.4 kW charger draws 62 A at 120 V (impossible on a standard outlet) but only 31 A at 240 V. Higher voltage means thinner wire, lower losses, and faster charging at the same circuit size.
What about 3-phase power (Europe and commercial sites)?
Three-phase delivers the same kW at one-third the current per phase. A 22 kW 3-phase 400 V circuit draws about 32 A per phase, versus ~92 A on single-phase 240 V. That is why European homes can charge much faster than typical US single-phase installs.
How does this relate to home wiring?
The amp result tells the electrician what breaker and wire gauge to size. 30 A continuous = 40 A breaker = 8 AWG copper. 48 A continuous = 60 A breaker = 6 AWG. See the Home Charger Amp Calculator for the full breaker + wire chart.