kW to Amps Calculator

On an Australian 400V three-phase supply, a 22 kW purely resistive load (PF 1.0) draws 31.8A per phase. For a standard 22 kW 3-phase induction motor (such as an elevator hoist, industrial air compressor, or large pump) operating at PF 0.85 and 91% efficiency, the full load current (FLA) is approximately 38A to 40A per phase. Under AS/NZS 3008, this typically requires 10mm² or 16mm² copper sub-mains protected by a 50A Type D circuit breaker.

A 5 kW three-phase motor operating at 400V with a typical power factor of 0.85 draws approximately 8.5 amps per phase. The calculation is: (5 × 1000) ÷ (400 × 1.732 × 0.85) = 8.49A. Most 5 kW motors have a nameplate FLA between 8.1A and 10.8A depending on their efficiency class.

Take the electrical input power in kW from the unit's compliance plate (not the cooling or heating capacity). Divide by 230V and then divide by the power factor. For example, a split system with 1.2 kW electrical input at PF 0.95 draws: (1,200) ÷ (230 × 0.95) = 5.49A. Always use the electrical input figure, not the cooling output rating.

kW (kilowatts) measures real power — the actual energy consumed and converted to useful work or heat. kVA (kilovolt-amps) measures apparent power — the total current flowing through the circuit multiplied by voltage. The relationship between them is: kW = kVA × Power Factor. For resistive loads at PF = 1.0, kW and kVA are identical. For inductive motor loads at PF = 0.85, a 15 kW load draws 17.65 kVA of apparent power.

At partial load, a motor's power factor drops significantly — sometimes below 0.60. Lower power factor means the motor draws more reactive current to maintain its magnetic field, even though the mechanical output is reduced. A 7.5 kW motor at half load might only produce 3.75 kW of shaft power but still draw nearly the same current as at full load because of the degraded power factor.

A 10 kW single-phase solar inverter at 230V with near-unity power factor (0.99 or higher) outputs approximately 43.5A. This is why most 10 kW single-phase inverter installations require a dedicated 50A or 63A supply circuit with 10 mm² or 16 mm² cabling from the inverter to the main switchboard, in accordance with AS/NZS 4777.1.

Not directly. Three-phase motors require three active conductors to create a rotating magnetic field. Running one on single-phase supply without modification will either not start at all or stall under load. A Variable Frequency Drive (VFD) can accept single-phase 230V input and output three-phase 230V to drive the motor, but the motor must be wired in delta (Δ) configuration and the VFD must be rated for the motor's full load current.

A 15 kW three-phase motor at 400V and PF 0.85 draws roughly 27.5A running current. The cable must be rated above 27.5A after applying derating factors, and the breaker rating must sit between the load current and the cable capacity. A 40A three-pole Type D MCB or MCCB is the standard choice — the Type D curve allows for motor starting inrush of up to 10 times the rated current without tripping.

No. The kW to amps formula calculates the current flowing through the circuit regardless of cable length. However, cable length directly affects voltage drop. Excessive voltage drop (more than 5% under AS/NZS 3000) reduces the voltage reaching the motor, which increases the current draw to compensate, potentially overloading the circuit. Always check voltage drop separately after calculating the base current.

Generators are rated in kVA (apparent power), not kW. To find the available amps, use: Amps = (kVA × 1000) ÷ (Voltage × √3) for three-phase, or Amps = (kVA × 1000) ÷ Voltage for single-phase. A 30 kVA three-phase generator at 400V delivers a maximum of 43.3A per phase. To find the real power available in kW, multiply kVA by the generator's rated power factor (usually 0.8), giving 24 kW.

If the nameplate is missing or illegible, use 0.85 as a safe general assumption for three-phase induction motors at full load. For single-phase capacitor-start motors, use 0.90 to 0.95. These are conservative estimates that will slightly overstate the current draw, which is safer than understating it when sizing cables and protective devices.

A typical commercial kitchen with ovens, fryers, exhaust hoods, coolrooms, and dishwashers can have a connected load of 40 to 80 kW across a mix of single-phase and three-phase circuits. The actual maximum demand is lower than the connected load because not all equipment runs simultaneously. Use the maximum demand calculator to apply diversity factors and calculate the actual switchboard load for supply authority connection applications.

Supply voltage fluctuates between 216V and 253V under Australian standards — higher voltage at the meter means lower current for the same kW load, and vice versa. Motor loading also affects the reading: a lightly loaded motor draws less current than its nameplate FLA. Temperature changes affect winding resistance. Power quality issues like voltage imbalance on three-phase circuits cause unequal phase currents. The calculated figure assumes nominal conditions; the clamp meter shows what's actually happening on site.