How Many Amps Is 3 kW?
3 kW = 3,000 W. At 240 V single-phase (PF 0.8): 15.6250 A. At 400 V three-phase (PF 0.8): 5.4127 A per phase. As DC at 240 V: 12.5000 A. Use the calculator below for any voltage or circuit type.
Real example: a 3 kW tankless water heater
3 kW single-phase is a common tankless / immersion water-heater and small-appliance rating. As a resistive load at 240 V it draws 12.5 A; at 120 V it would be 25 A. (3 kW is also roughly 4 HP of motor output.)
3 kW to Amps — Reference Chart
| Circuit | Voltage | PF | Amps |
|---|---|---|---|
| DC | 120 V | — | 25.0000 A |
| DC | 240 V | — | 12.5000 A |
| DC | 480 V | — | 6.2500 A |
| AC 1Ø | 120 V | 1.0 | 25.0000 A |
| AC 1Ø | 240 V | 1.0 | 12.5000 A |
| AC 1Ø | 240 V | 0.8 | 15.6250 A |
| AC 3Ø (L-L) | 208 V | 0.8 | 10.4090 A |
| AC 3Ø (L-L) | 400 V | 0.8 | 5.4127 A |
| AC 3Ø (L-L) | 480 V | 0.8 | 4.5105 A |
Wire & breaker: At 240 V, 3 kW resistive draws 12.5 A; at NEC 125% that is 15.6 A, so a 20 A breaker on 12 AWG copper is correct. Always confirm with an electrician. Background: watts vs amps.
Frequently Asked Questions
How many amps is 3 kW at 240V single-phase?
3 kW at 240V DC or PF 1 = (3 × 1,000) ÷ 240 = 12.5000 amps. For AC single-phase with PF 0.8: 3,000 ÷ (240 × 0.8) = 15.6250 amps.
How many amps is 3 kW on a 400V three-phase supply?
3 kW on 400V three-phase at PF 0.8 = (3 × 1,000) ÷ (√3 × 400 × 0.8) = 5.4127 amps per phase. At unity PF: 4.3301 amps.
What breaker size does a 3 kW water heater need?
A 3 kW resistive heater at 240 V draws 12.5 A. Continuous loads are sized at 125%: 12.5 × 1.25 = 15.6 A, so a 20 A breaker with 12 AWG copper is the right choice. Reverse the calc with amps to kW.