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Power Factor Calculator with Capacitor kVAR for Correction

Enter kW and kVA, or meter readings of watts, volts and amps. You get the power factor, phase angle, reactive power and the capacitor needed to correct it.

Power factor

0.8

Low
Phase angle
36.9 °
Reactive power
6 kVAR
Capacitor needed
3.371 kVAR

For guidance only. Electrical work must follow IS 732 and the cable makers’ tables, and be done or checked by a licensed electrician.

Capacitor kVAR = kW × (tan φ1 − tan φ2) at 50 Hz.

Show working
  1. PF = 8 ÷ 10 = 0.8
  2. Q = √(10² − 8²) = 6 kVAR
  3. Qc = 8 × (0.75 − 0.3287) = 3.371 kVAR

How to use

  1. Choose kW and kVA, or watts, volts and amps.
  2. Enter the values (for three-phase use line voltage).
  3. Set the target power factor to see capacitor kVAR.

Good to know

Power factor = real power ÷ apparent power = kW ÷ kVA = cos φ. Reactive power kVAR = √(kVA² − kW²). A low power factor means more current for the same work, so cables, transformers and bills are loaded more.

Capacitor needed to go from PF1 to PF2: kVAR = kW × (tan φ1 − tan φ2). For single-phase at 50 Hz, capacitance C = kVAR × 1000 ÷ (2π × 50 × V²); for a three-phase delta-connected bank, per phase C = kVAR × 1000 ÷ (3 × 2π × 50 × V²).

Many Indian DISCOMs bill commercial and industrial users in kVAh or apply PF incentives and penalties, so correction can save money. Capacitor banks must be sized and installed by a qualified electrician; over-correction (leading PF) is also penalised in some tariffs.

Questions

What is a good power factor?

0.95 or above is good; many tariffs penalise below about 0.9. Check your DISCOM’s rules.

How much capacitor for 8 kW at PF 0.8 to reach 0.95?

8 × (0.75 − 0.329) = 3.37 kVAR.

How do I find PF from a meter?

PF = watts ÷ (volts × amps); for three-phase divide by √3 × V × I.

Why is my power factor low?

Induction motors, pumps, ACs and old tube-light chokes draw reactive current.

Is too much capacitance bad?

Yes. It makes the power factor leading and can cause over-voltage; size correction carefully.

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