How do I calculate the power factor?
  • Power Supplies
  • >
  • AC-DC Power Supplies

A. Power factor is the ratio of active power to apparent power. The larger the active power, the higher the power factor. The calculation method is listed below:

Power factor = Active power (W) / Apparent power (VA)

Apparent power: Active power + Reactive power
Active power: Power actually consumed by the device (load side)
Reactive power: Power not consumed by device (load side)

Calculation example (15W-24V output model): When obtaining the power factor from the actual usage environment
・Numerical values read from the actual usage environment: Specifications
Input voltage=100VAC
Output voltage=24V
Output current=0.65A (100%)

・Numerical values read from the data below:
Input current=0.33A

・Calculated numerical value: Power factor, active power

Active power = Output voltage × Output current ÷ Efficiency = 24 × 0.65/85% = 18.4W
Apparent power = Input voltage × Input current = 100 × 0.33 = 33VA
Power factor = Active power/Apparent power = 18.4/33 = 0.55

Figure 1