Power Factor Correction Calculator

Compute the capacitor size needed to move from your current power factor to a target power factor. Includes kVAR, estimated µF, current before/after, and Show Work.

How to Use

  1. Enter your real power (kW) and your initial PF (0–1).
  2. Set the target PF you want to reach.
  3. Select single-phase or three-phase, your voltage, and frequency.
  4. Review required capacitor kVAR and the estimated capacitance (µF).
Before / After
kW stays the same; PF correction reduces kVAR and kVA.
Capacitor
—
Estimated C
—
kVA (before)
—
kVA (after)
—
Status: —
P (kW)
—
Q before (kVAR)
—
Q after (kVAR)
—
ΔI (amps)
—

Tip: This calculator estimates capacitor µF assuming a shunt capacitor bank at the selected voltage/frequency. Always verify with equipment specs and local codes.

Inputs & Settings
Enter kW + PF values. Choose phase, voltage, and frequency.
Use real power (kW), not kVA.
Most inductive loads are lagging (motors, transformers).
Usually target is lagging (e.g., 0.95). Avoid over-correction.
Use the voltage that matches where the capacitor bank connects.
Examples: 120, 240, 480, 600, 230, 400.
North America is typically 60 Hz. Many other regions are 50 Hz.
Show Work (step-by-step)
—
Work is shown in base units (kW, kVA, kVAR, V, A, Hz). Capacitance is an estimate; always confirm capacitor bank ratings.

Formulas Used

Power factor: PF = kW / kVA

  • Apparent power: kVA = kW / PF
  • Reactive power: kVAR = kW × tan(acos(PF))
  • Capacitor kVAR needed: Qc = kW × (tan(acos(PF1)) − tan(acos(PF2))) (sign depends on lag/lead)
  • Current:
    • Single-phase: I = (kVA × 1000) / V
    • Three-phase (line-to-line): I = (kVA × 1000) / (√3 × V_LL)
  • Capacitance estimate (shunt): computed from Qc, voltage, and frequency in tool JS.
If your target PF is “leading”, you may be over-correcting; use caution.

FAQ

Why does power factor correction reduce current?

For the same real power (kW), improving PF reduces apparent power (kVA). Lower kVA at the same voltage means lower RMS current.

Does PF correction reduce kW?

Not directly. Real work (kW) is set by the load. PF correction mainly reduces kVAR and kVA, which can reduce losses and utility penalties.

What is “kVAR” in plain terms?

kVAR is reactive power — energy that sloshes between the source and inductive/capacitive elements. It increases current but does not do useful work.

Can I over-correct power factor?

Yes. A leading PF can cause voltage rise and resonance issues in some systems. Use staged banks and consult equipment specs.

Tool Info

Last updated:

Updates may include additional wiring modes, capacitor bank configuration options, and edge-case handling.