What is power factor correction?

Power factor is the ratio of real power (kW) to apparent power (kVA). Inductive loads like motors and transformers draw lagging reactive current that raises apparent power without doing useful work. Connecting capacitors in parallel supplies the reactive current locally, reducing the lagging current drawn from the utility and raising the power factor toward 1.0.

Why correct to 0.95 and not 1.0?

Most utilities require a minimum of 0.90–0.95 lagging. Correcting all the way to unity (1.0) or beyond (leading) can cause voltage rise on lightly loaded feeders and may actually incur penalties. 0.95–0.98 is the practical target for most industrial sites.

What is the formula used?

Q_c = P × (tan(arccos(PF₁)) − tan(arccos(PF₂))). For single-phase: C = Q_c / (2π × f × V²). For three-phase (delta-connected): C = Q_c / (3 × 2π × f × V_LL²). For three-phase (star/wye): C = Q_c / (2π × f × (V_LL/√3)²) per phase, giving the same total Q_c.

Does this work for three-phase systems?

Yes. Select "Three-phase" and enter the line-to-line voltage. The calculator gives the total three-phase kVAR required and the per-phase capacitance for a star (Y) or delta (Δ) connected bank.

What if my existing power factor is already above the target?

If PF₁ ≥ PF₂ no correction is needed. The calculator will show 0 kVAR required and display a note.

Power Factor Correction Calculator

Find the capacitor bank size (kVAR and µF) needed to improve power factor to a target value.

System Parameters

System Type

Single-phase Three-phase

Real Power (kW)

Supply Voltage (V) line voltage

Frequency (Hz)

Existing Power Factor (0.01 – 0.99)

Target Power Factor (0.01 – 1.00)

Correction Required

— kVAR

Reactive power the capacitor bank must supply

Cap. (Single-ph / Per-phase Y)

— µF

Cap. Per-phase (Δ delta)

— µF

Power Summary

Real Power (P)	—	kW
Apparent Power — Before (S₁)	—	kVA
Apparent Power — After (S₂)	—	kVA
Reactive Power — Before (Q₁)	—	kVAR
Reactive Power — After (Q₂)	—	kVAR
kVA Demand Reduction	—	kVA

Formula: Q_c = P × (tan φ₁ − tan φ₂) | C_Y = Q_c / (2π · f · V_phase²) | C_Δ = Q_c / (3 · 2π · f · V_LL²)

Enter system parameters and click Calculate.

Summary

Find the capacitor bank size (kVAR and µF) needed to improve power factor to a target value.

How it works

Enter the real load power in kilowatts (kW).
Enter the supply voltage (line-to-line for three-phase, or line voltage for single-phase) and frequency.
Choose single-phase or three-phase system.
Enter the existing (uncorrected) power factor and the target power factor.
The calculator computes the required reactive power Q_c = P × (tan φ₁ − tan φ₂).
It then converts Q_c to capacitance: C = Q_c / (2π × f × V²) for single-phase.

Use cases

Size a capacitor bank to avoid utility power-factor penalties.
Reduce apparent power (kVA) demand on distribution transformers.
Determine capacitor requirements when upgrading industrial motor loads.
Verify existing capacitor bank adequacy after adding new equipment.
Teach AC circuit power factor concepts in engineering courses.
Pre-screen correction needs before calling an electrical contractor.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu