How to convert kW to amps (the formulas)
Amps come from power and voltage. Kilowatts are just watts ÷ 1000, so every formula starts by multiplying kW back to watts, then dividing by the voltage (and by power factor for AC). There are three cases:
| System | Formula | Example |
|---|---|---|
| DC | I = kW × 1000 ÷ V | 10 kW ÷ 240 V = 41.67 A |
| AC single-phase | I = kW × 1000 ÷ (V × PF) | 10 kW, 240 V, PF 1 = 41.67 A |
| AC three-phase | I = kW × 1000 ÷ (√3 × V × PF) | 10 kW, 480 V, PF 1 = 12.03 A |
The × 1000 converts kilowatts to watts. The √3 (about 1.732) in the three-phase formula comes from the geometry of three-phase power — it's why the same kilowatts draw fewer amps per line on a three-phase system.
Power factor: why kW isn't the whole story
Kilowatts measure real power — the work actually done. But the current a load pulls depends on apparent power (kVA), and the two only match when the power factor is 1.0. Resistive loads like heaters and incandescent lamps are PF 1.0; motors and other reactive loads run around 0.8, which means they pull more amps for the same kilowatts.
A 10 kW load at 480 V three-phase:
• at PF 1.0 (resistive) → 12.03 A
• at PF 0.8 (motor) → 15.04 A
Same kilowatts, 25% more current — always use the motor's real power factor from its nameplate.
Single-phase vs three-phase
Homes are single-phase (120/240 V); commercial and industrial services are often three-phase (208/480 V). Because the three-phase formula divides by an extra √3, the same kilowatts draw fewer amps per conductor on three-phase — one reason big equipment is wired that way. Here's the same 10 kW across common systems:
| 10 kW at PF 1.0 | Voltage | Amps |
|---|---|---|
| Single-phase | 120 V | 83.33 A |
| Single-phase | 240 V | 41.67 A |
| Three-phase | 208 V | 27.76 A |
| Three-phase | 480 V | 12.03 A |
kW to amps reference table
Common kilowatt ratings converted to amps at power factor 1.0 (divide by your PF for motors):
| Power | 120 V (1φ) | 240 V (1φ) | 208 V (3φ) | 480 V (3φ) |
|---|---|---|---|---|
| 1 kW | 8.33 A | 4.17 A | 2.78 A | 1.20 A |
| 2 kW | 16.67 A | 8.33 A | 5.55 A | 2.41 A |
| 5 kW | 41.67 A | 20.83 A | 13.88 A | 6.01 A |
| 10 kW | 83.33 A | 41.67 A | 27.76 A | 12.03 A |
| 15 kW | 125 A | 62.5 A | 41.64 A | 18.04 A |
| 20 kW | 166.67 A | 83.33 A | 55.51 A | 24.06 A |
Generators are rated in kW (real power) and often kVA (apparent power) — this converter turns that rating into the amps each output can supply, so you can match it to a transfer switch or panel. If your rating is in kVA instead of kW, it already includes power factor: use amps = kVA × 1000 ÷ V (÷ √3 × V for three-phase) with no separate PF.
From amps to a circuit: size the wire and breaker
Once you know the amps, the circuit needs the right breaker and wire. Remember the NEC 125% rule for continuous loads (running three hours or more) — the breaker and conductor are sized to 125% of the current, so a 41.7 A continuous load wants a 60 A circuit, not a 50. Run your number through the Wire Size Calculator and the Breaker Size Calculator, and the AWG ampacity chart has the conductor ratings.
Frequently asked questions
ConversionsWhat is the formula to convert kW to amps?
ConversionsHow many amps is 1 kW at 240 volts?
ConversionsHow many amps is 10 kW at 240 volts?
ConversionsHow many amps is 10 kW three-phase?
ConversionsHow many amps is 7000 watts?
ConversionsDoes power factor change the amps?
ConversionsIs kW to amps different for three-phase?
ConversionsHow do I convert amps back to kW?
This calculator gives estimates from the standard power formulas. Real loads vary with power factor, efficiency, and voltage — always use the equipment nameplate for design, and follow the NEC and your local authority having jurisdiction (AHJ) when sizing circuits. When in doubt, hire a licensed electrician.