Power Factor Calculator

Calculate power factor, real power, reactive power, and apparent power. Determine capacitor size for power factor correction.

Power Factor Result

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Power Values

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Analysis

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Power Triangle

Real Power (kW)
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+
Reactive Power (kVAR)
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=
Apparent Power (kVA)
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Power Factor Angle: -

Power Factor Formula

PF = Real Power / Apparent Power

PF = cos(θ) where θ is the angle between voltage and current

Apparent Power (kVA): S = √(P² + Q²)

Reactive Power (kVAR): Q = √(S² - P²)

Power Factor Categories

  • Unity (1.0): Perfect efficiency
  • 0.95-1.0: Excellent
  • 0.90-0.95: Good
  • 0.80-0.90: Fair
  • <0.80: Poor - Correction recommended

Why Correct Power Factor?

  • Reduce utility penalties
  • Lower electricity bills
  • Increase system capacity
  • Reduce line losses
  • Improve voltage regulation

Frequently Asked Questions

What is power factor?

Power factor is the ratio of real power (kW) to apparent power (kVA). It measures how effectively electrical power is being used. A power factor of 1.0 (unity) means all power is being used effectively, while lower values indicate inefficiency.

How do you calculate power factor?

Power Factor = Real Power (kW) / Apparent Power (kVA)

For example, if you have 100 kW of real power and 125 kVA of apparent power: PF = 100/125 = 0.8

What is a good power factor?

A power factor of 0.95 or higher is considered excellent. Most utilities charge penalties for power factors below 0.85. Commercial and industrial facilities typically aim for 0.90-0.95.

How do I calculate capacitor size for PF correction?

Use the formula: Qc = P × (tan(θ1) - tan(θ2)) where:

  • Qc = Required reactive power (kVAR)
  • P = Real power (kW)
  • θ1 = Angle for current PF
  • θ2 = Angle for desired PF

What causes low power factor?

Common causes include:

  • Inductive loads (motors, transformers)
  • Fluorescent lighting with magnetic ballasts
  • Welding equipment
  • Under-loaded motors
  • Non-linear loads (harmonics)

What is the difference between kW, kVAR, and kVA?

  • kW (Real Power): Actual power doing work
  • kVAR (Reactive Power): Power used to maintain magnetic fields
  • kVA (Apparent Power): Total power supplied

These three form the power triangle: kVA² = kW² + kVAR²

How can I improve power factor?

  • Install power factor correction capacitors
  • Use synchronous motors
  • Avoid under-loaded motors
  • Use LED lighting instead of fluorescent
  • Install harmonic filters