Power Factor Correction Calculator
How much capacitor kVAR it takes to lift your power factor — and what that buys you in lower apparent power, less current and smaller demand charges. Enter the real power and the before-and-after power factor.
Why Power Factor Costs You Money
Real power (kW) does the work; reactive power (kVAR) just sloshes back and forth magnetizing motors and transformers. Together they make apparent power (kVA), and your wires, transformers and utility bill are sized on the kVA, not the kW. A low power factor means you are paying to move current that does no useful work. Adding capacitors supplies the reactive power locally, so the rest of the system does not have to.
Sizing the Capacitors
where φ₁ and φ₂ are the angles whose cosines are the existing and target power factors. The capacitor bank supplies the difference in reactive power. Because real power is unchanged, the apparent power and current both fall in proportion to PF₁ / PF₂.
What Correction Buys You
Raising the power factor cuts the current flowing through every transformer, breaker and cable upstream — freeing capacity for more load — reduces voltage drop and losses, and on most commercial tariffs trims the demand or power-factor penalty on the bill. Going from 0.75 to 0.95 alone drops the current by about a fifth.
Frequently Asked Questions
Why not correct all the way to 1.0?
Capacitors come in fixed steps and load varies, so aiming for unity risks overcorrecting into a leading power factor, which causes its own voltage and stability problems. Most targets land around 0.95.
Does correction reduce my kWh?
Not directly – real energy use is the same. It reduces apparent power and current, which is what utilities penalize through demand and power-factor charges, and it lowers resistive losses slightly.
Fixed or automatic capacitors?
A steady load can use a fixed bank; a varying load needs an automatic bank that switches steps in and out to track the load and avoid overcorrection.
Related calculators
- Three-Phase Power Calculator — the kW, kVA and kVAR relationship.
- Motor FLA Calculator — motors are the usual source of poor power factor.
- Wire Size Calculator — lower current can mean smaller conductors.
- Engineering Unit Converter — power and energy units.