About

When sizing industrial equipment, backup generators, or main service panels, power is almost always rated in Kilowatts (kW) rather than Watts. This calculator scales standard power formulas to handle larger loads. It is engineered to handle the complexity of Three-Phase power systems, specifically addressing the √3 factor required for Line-to-Line voltage inputs, which is standard in commercial and industrial settings. Accurate conversion ensures you don't undersize a generator or overload a transformer.

Formulas

The power formulas include division by 1000 to convert Watts to Kilowatts:

1. DC Circuits:

PkW = I × V1000

2. AC Single-Phase:

PkW = I × V × PF1000

3. AC Three-Phase (Line-to-Line):

PkW = √3 × I × VL-L × PF1000

Note: √3 ≈ 1.732. Use the voltage measured between two hot wires (Line-to-Line) for the 3-Phase formula.

Reference Data

System	Volts (V)	Amps (I)	PF	Result (kW)
AC 1-Phase	120	15	1.0	1.8 kW
AC 1-Phase	240	50	0.9	10.8 kW
AC 3-Phase	208	30	0.8	8.65 kW
AC 3-Phase	480	100	0.9	74.82 kW
AC 3-Phase	415	63	0.85	38.49 kW
DC System	48	200	N/A	9.6 kW
AC 1-Phase	230	32	1.0	7.36 kW
AC 3-Phase	380	16	0.8	8.42 kW

Frequently Asked Questions

Single-phase power is used in most homes (2 wires + ground). Three-phase power is used in industrial settings (3 or 4 wires) to deliver more consistent power for heavy motors. Three-phase calculations include a multiplier of approximately 1.732.

For 3-phase equipment, the voltage rating on the nameplate is typically Line-to-Line (e.g., 480V or 208V). If you are calculating the total power of the machine, use the 3-phase formula with Line-to-Line voltage.

kW measures Real Power (useful work). If you ignore the Power Factor, you are calculating kVA (Apparent Power). For resistive loads like heaters, they are the same (PF=1). For motors, kW is always lower than kVA.

DC calculations are simple: Amps × Volts ÷ 1000. There is no frequency or phase shift, so the Power Factor is not applicable.