AC power analysis tool
Power factor calculator
Calculate real, reactive and apparent power, displacement power factor, phase angle and estimated line current. For lagging loads, estimate the ideal capacitive kvar needed to reach a higher target power factor.
Power factor result
Real power
100 kW
Reactive power
75 kvar
lagging
Apparent power
125 kVA
Power factor
0.8
lagging displacement PF
Phase angle
36.87°
Estimated line current
180.422 A
Sinusoidal power result
The result treats power factor as displacement power factor. Use a power-quality measurement for distorted or unbalanced waveforms.
Power triangle
Real, reactive and apparent power for a sinusoidal steady-state model.
PF = P / S
How to use the power factor calculator
Choose the input pair that matches the quantities you know, then keep the voltage definition consistent with the selected circuit system.
- 01
Choose the known power values
Use kW and power factor, kW and kvar, or the correction mode with an existing and target power factor.
- 02
Identify lagging or leading behavior
Inductive loads normally have lagging current and positive reactive power. Capacitive loads have leading current and negative reactive power.
- 03
Select the circuit system and voltage
For a balanced three-phase load enter line-to-line voltage. For a single-phase load enter the voltage across the load.
- 04
Review the triangle and engineering limits
Compare kW, kvar, kVA, current and phase angle. Treat correction kvar as a first-pass estimate until field conditions are verified.
Power factor and AC power relationships
The calculator uses the sinusoidal steady-state power triangle. In this ideal model, displacement power factor is the cosine of the angle between voltage and current.
Power factor
PF = P / S = cos φ
Power triangle
S² = P² + Q²
Reactive power
Q = P × tan φ
Single-phase apparent power
S = V × I
Balanced three-phase apparent power
S = √3 × VL × IL
Ideal correction requirement
Qc = P × (tan φ1 − tan φ2)
Real power P is measured in kW, reactive power Q in kvar and apparent power S in kVA. The sign of Q distinguishes lagging and leading behavior. Harmonics, unbalance and nonsinusoidal current can make true power factor lower than the displacement power factor described by the simple triangle.
Power-factor correction does not reduce the real power demanded by an unchanged load. Before selecting or installing capacitor banks, measure the operating load profile and harmonics, evaluate resonance and switching transients, confirm protection and discharge requirements, and follow the utility and equipment manufacturer guidance.
Checks before applying a correction value
A useful correction design depends on measured operating conditions, not only one nameplate or billing value.
Distinguish true and displacement power factor
A basic meter or nameplate value may not reveal harmonic distortion. Use a power-quality instrument when nonlinear loads are present.
Check harmonics and resonance
Capacitors interact with system inductance. Evaluate resonant frequency and consider detuned equipment where harmonic current is significant.
Avoid overcorrection
Excess fixed capacitance can produce a leading power factor during light load and may conflict with utility requirements or equipment limits.
Account for load variation
Use staged or automatically controlled correction when the reactive-power demand changes materially over time.
Verify voltage, duty and protection ratings
Confirm capacitor voltage, ambient temperature, switching duty, short-circuit protection and discharge provisions against applicable standards and manufacturer data.
Check the utility tariff and metering method
Demand penalties and acceptable power-factor targets vary. Correct to the measured billing condition rather than assuming one universal target.
Power factor calculator questions
What do leading and lagging power factor mean?
Lagging current is normally associated with inductive loads and positive kvar. Leading current is normally associated with capacitive behavior and negative kvar.
What is the difference between kW, kvar and kVA?
kW is real power converted to useful work or heat, kvar represents reactive power exchanged with electric or magnetic fields, and kVA is the magnitude of their combined apparent power.
Does power-factor correction reduce kWh consumption?
It does not reduce the real energy required by an unchanged ideal load. It can reduce current and upstream I²R losses and may reduce utility demand or power-factor charges, depending on the installation and tariff.
Why does line current fall when power factor improves?
At the same real power and voltage, higher power factor means lower apparent power. Because current follows apparent power, the supply current decreases.
Why can measured true power factor differ from this result?
The simple power triangle describes displacement power factor for sinusoidal waveforms. Harmonic current and voltage distortion add distortion power factor, so a power-quality instrument can report a lower true value.
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