kW to Amps Calculator

Divide the power in watts by √3, the line-to-line voltage and the power factor: I = P × 1000 / (√3 × V × cos φ). 10 kW at 400 V and a power factor of 0.8 draws about 18.0 A per line.

Divide the power in watts by the voltage and the power factor: I = P × 1000 / (V × cos φ). 10 kW at 230 V and 0.8 draws about 54.3 A; a purely resistive 10 kW load (power factor 1) draws 43.5 A.

At 230 V single-phase and unity power factor, 1 kW is about 4.35 A. At 400 V three-phase it is about 1.44 A per line at unity power factor, or 1.80 A at a power factor of 0.8.

Use the equipment's nameplate figure when you have it. Resistive loads such as heaters and hot water elements are 1.0; induction motors run around 0.8 to 0.9 at full load; 0.8 is the usual assumption when nothing better is known. DC has no power factor.

In a balanced three-phase system the line-to-line voltage is √3 times the phase voltage, and the total power is three times the power in each phase. Writing the power in terms of the line voltage and line current leaves a factor of √3 ≈ 1.732.

Not directly. A motor's kW rating is its shaft output, so the electrical input is higher by the efficiency. Use the motor full load current calculator, or better, the nameplate current.

No. The current is the load's design current. The cable is then sized for that current after derating, and the protective device rated between the two, as AS/NZS 3000 Clause 2.5 requires.