What is power factor correction?

Power factor correction adds capacitive reactive power to cancel inductive reactive power drawn by motors and transformers. This brings the power factor closer to unity, reducing wasted current and lowering electricity bills.

Why is the result in kVAR?

Capacitor banks are rated in kilovolt-amperes reactive (kVAR), which is the unit of reactive power. You need to supply enough kVAR capacitively to offset the inductive kVAR of the load and raise the power factor to the target level.

What target power factor should I use?

Most utilities require a minimum of 0.90 to 0.95 to avoid penalty surcharges. Targeting 0.95–0.98 is typical for industrial sites. Going above 0.99 yields diminishing returns and risks leading (over-corrected) power factor.

Does this apply to three-phase and single-phase systems?

Yes. The formula Q = P × (tan φ₁ − tan φ₂) is valid for both. For three-phase, enter the total three-phase kW load. The kVAR result is the total bank rating needed across all three phases.

How do I convert kVAR to capacitor capacitance (µF)?

For a single-phase system: C = Q × 10⁶ / (2π × f × V²). For three-phase: divide kVAR by 3 first to get per-phase kVAR. This calculator focuses on kVAR sizing; use the result to select standard capacitor bank steps.

What if my load varies throughout the day?

Size for the average or peak inductive load that causes penalty charges. Many installations use automatic power factor controllers (APFC) that switch capacitor bank steps in and out as load changes.

Capacitor Bank Sizing

Enter load kW, existing power factor, and target power factor to find the required capacitor bank size in kVAR.

Input Parameters

Active Load (kW)

Total active (real) power of the load in kilowatts.

Existing Power Factor

Current (lagging) power factor, between 0.01 and 1.00.

Target Power Factor

Desired power factor after correction (must exceed existing).

Results

Enter load and power factor values, then click Calculate.

Summary

This calculator determines how many kVAR of capacitive reactive power you need to install to raise a lagging power factor from its current value to a desired target. It uses the standard electrical engineering formula Q = P × (tan φ₁ − tan φ₂), where P is the active load in kW and φ₁, φ₂ are the phase angles corresponding to the existing and target power factors. Results include required capacitor bank size, reactive power before and after correction, and the reduction in apparent power (kVA).

How it works

Enter the active load in kilowatts (kW).
Enter the existing (current) power factor as a decimal between 0.01 and 1.00.
Enter the target (desired) power factor, which must be higher than the existing value.
The calculator applies the standard formula: Q = P × (tan φ₁ − tan φ₂).
Results show required kVAR, the reactive power before and after correction, and apparent power change.

Use cases

Size capacitor banks for industrial motor loads.
Calculate reactive compensation for commercial buildings with low power factor.
Verify utility power factor penalty thresholds before billing cycles.
Estimate capacitor bank investment for energy cost reduction.
Plan reactive power compensation for generator sets.
Design power factor correction for variable-frequency drive systems.

Frequently Asked Questions

Last updated: 2026-06-19 · Reviewed by Nham Vu