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Power Factor Correction Calculator & Capacitor Sizing

Calculate electrical efficiency and determine required kVAR for power factor correction. Optimizes industrial power usage to avoid utility penalties.

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About

Industrial facilities often face surcharges on electricity bills due to poor Power Factor (PF). This ratio of Real Power to Apparent Power indicates how effectively electrical current converts into useful work output. A low PF causes unnecessary strain on the distribution network. Correcting this metric reduces demand charges and increases system capacity.

This tool calculates the precise reactive power (kVAR) needed to improve the system from an initial lagging PF to a desired target. This correction is achieved by installing capacitor banks parallel to the load. The calculation uses trigonometric relationships in the power triangle to size these capacitors accurately, preventing over-correction which can lead to dangerous over-voltages.

power-factor electrical-engineering kvar capacitors energy-efficiency

Formulas

The required capacitor rating Qc is derived from the difference in the tangent of the phase angles:

Qc = P × (tan(θ1) − tan(θ2))

Where the phase angles are derived from the Power Factor (cosine of the angle):

θ = arccos(PF)

Apparent Power S is calculated as:

S = PPF

Reference Data

TermSymbolUnitDefinition
Real PowerPkWThe actual power consumed by the equipment to do useful work.
Apparent PowerSkVAThe vector sum of Real and Reactive power. Total power drawn.
Reactive PowerQkVARPower oscillating between source and load (magnetic fields).
Power FactorPF0-1Efficiency ratio PS. Target is usually 0.95+.

Frequently Asked Questions

Raising the PF above 1.0 (leading power factor) causes the system to supply reactive power back to the grid. This can result in dangerous over-voltage conditions, harmonic amplification, and potential damage to insulation and sensitive electronics.
Low PF requires the utility to supply more current (Amps) to deliver the same amount of Real Power (kW). This excess current causes heating losses in transmission lines and transformers, forcing the utility to install larger infrastructure.
No. Fixed capacitors provide a constant kVAR, but if your load varies significantly (e.g., motors turning on and off), you may need an Automatic Power Factor Correction (APFC) bank to step capacitors in and out dynamically.