Power factor correction calculator
Calculate the reactive power (kvar) of a capacitor bank needed to improve the power factor of a load.
How it is calculated
Qc = P × (tan φ₁ − tan φ₂), where tan φ = √(1 − PF²) ÷ PF for each power factor.
Worked example
P = 100 kW, PF from 0.70 to 0.95: tan φ₁ = 1.020, tan φ₂ = 0.329, so Qc = 100 × 0.691 = 69.15 kvar.
Steps
- Enter the active power from the meter or the load list.
- Enter the existing power factor from the bill or power meter.
- Enter the target power factor, then read the kvar and round to a standard bank size.
Frequently asked questions
What target PF should I use?
Many utility tariffs penalize a PF below 0.90 to 0.95. Check your tariff before setting the target.
Can I correct to exactly 1.0?
You can, but it can cause overcorrection at light load. Target 0.95 to 0.98 in most plants.
Do I need detuning reactors?
Yes, if there are harmonics from drives or rectifiers. Capacitors alone can resonate with them.
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References
Reactive power relation Q = P(tan φ₁ − tan φ₂); IEEE 18 for shunt capacitor standards; utility tariff rules for penalties.
Estimates for information only. Verify critical values with a qualified engineer or your supplier standards.