Power Factor Correction (kVAR) Calculator
Calculate the required capacitor bank size (kVAR) to correct a lagging power factor to a target value, reducing reactive power charges.
Results
What is it?
Power factor correction uses capacitor banks to supply reactive power locally, reducing the reactive current demand from the utility. The required capacitor size: Q_c = P × (tan φ₁ − tan φ₂) where φ₁ and φ₂ are the existing and target power factor angles.
How to use
Enter your total real power load in kW, your current (poor) power factor, and your target power factor (typically 0.95–0.98 to avoid penalty charges). The result is the kVAR rating of capacitors to install.
Example scenario
A factory has 100 kW load at PF = 0.72 (lagging). Target PF = 0.95. Q_c = 100 × (tan(43.9°) − tan(18.2°)) = 100 × (0.966 − 0.329) = 63.7 kVAR. Installing a 63.7 kVAR capacitor bank corrects the power factor to 0.95, reducing apparent power from 139 to 105 kVA.
Pro tip
Most utilities levy a power factor penalty below 0.9 or 0.95. Capacitor banks pay back in 1–3 years through reduced demand charges. For sites with variable loads (motors cycling on/off), use automatic (APFC) panels with switching stages rather than fixed capacitors, to avoid leading power factor and over-voltage.