Power Factor Correction Calculator

Find the capacitor kVAR needed to raise power factor to a target, and how much it cuts apparent power and current.

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kVAR Needed

kVA before
kVA after
Current before
Current after
Current reduced
Capacitance
Capacitor Bank

Saved Loads

Items you add are saved in this browser.

Load	kW	PF From	PF To	kVAR	Remove

How Power Factor Correction Works

Power factor is the share of apparent power (kVA) that does useful work (kW). Motors and transformers draw extra reactive power (kVAR) to build their magnetic fields, which lowers the power factor and makes the system carry more current than the real load needs. Capacitors supply that reactive power locally, cutting the current from the utility.

kVAR needed = kW × (tan φ₁ − tan φ₂), where φ = arccos(power factor)

kVA = kW ÷ PF Current (3-phase) = kVA × 1,000 ÷ (1.732 × V)

Capacitance (µF, per phase, delta) = kVAR × 10⁹ ÷ (3 × 2π × f × V²)

Worked Example

A 100 kW load at 0.70 power factor draws 100 ÷ 0.70 = 142.9 kVA. At 0.70, tan φ is 1.020; at 0.95, it's 0.329. So correcting to 0.95 takes 100 × (1.020 − 0.329) = 69.2 kVAR of capacitors, and cuts the apparent power to 100 ÷ 0.95 = 105.3 kVA, about 26% less current.

kVAR Multiplier Table

Multiply kW by this number to get the kVAR needed.

From PF	To 0.90	To 0.95	To 0.98	To 1.00

Tips

Many utilities charge a penalty when power factor falls below a set level, often around 0.90 to 0.95, so check your tariff. Don't overcorrect: a leading power factor can raise voltage and cause problems, especially at light load. Capacitors near large motors should be sized to the motor maker's tables to avoid self-excitation, and harmonics from drives can overheat capacitors. Have an electrical engineer design correction for large systems.