Power Factor Correction Calculator
Low power factor means your supply carries more current than the useful work requires — bigger cables, bigger transformers, and often a penalty on the bill. A capacitor bank corrects it. Enter the real power and the present and target power factors, and this calculator returns the capacitor size in kVAR.
Formula: kVAR = P × (tan φ₁ − tan φ₂), where φ = arccos(pf) · New apparent power = P ÷ target pf
Worked example: a 100 kW load at 0.75 pf corrected to 0.95 pf: tan(arccos 0.75) ≈ 0.882, tan(arccos 0.95) ≈ 0.329, so kVAR = 100 × (0.882 − 0.329) ≈ 55.3 kVAR. Apparent power falls from 133.3 kVA to 105.3 kVA — 28 kVA of freed capacity, which is often worth more than the penalty saving alone. Correcting to exactly 1.0 is rarely wise: it risks leading power factor and resonance, so 0.95 is the usual target.
For the kW/kVA/kVAR triangle itself, use the three-phase power calculator.
Frequently asked questions
What is power factor, simply?
The ratio of useful power (kW) to apparent power (kVA). A motor at 0.8 pf draws 25% more current than the same kW at unity pf — that extra current heats cables and fills transformers without doing work.
Why not correct all the way to 1.0?
Over-correction creates a leading power factor, which can raise voltage, stress capacitors, and risk resonance with transformer inductance. Utilities and designers typically target 0.95.
Do capacitors save energy?
They save capacity and reduce losses in your own cables and transformers, and they remove utility pf penalties. They do not reduce the kW your load consumes — the motor still does the same work.