Why power factor correction saves money
A real-world load draws two kinds of power: the real power (kW) that does useful work and the reactive power (kVAR) that magnetises motors and transformers but does no work. Their vector sum is the apparent power (kVA) the utility must actually deliver, and many utilities bill on it or penalise a low power factor. A capacitor bank locally supplies the reactive power so the utility no longer has to, raising the power factor toward 1.0 and shrinking the kVA — and the bill — without changing the useful work the load performs.
How it works
The required capacitor reactive power follows directly from the power triangle:
Q_c = P × (tan θ1 − tan θ2)Here θ₁ = arccos(existing PF) and θ₂ = arccos(target PF). Because the capacitor cancels part of the load’s reactive power, the apparent power falls from P / PF1 to P / PF2. The tool computes the exact kVAR needed, then picks the nearest standard capacitor size at or above that value and recomputes the power factor you would actually land on after installing that fixed step, since real banks come in discrete sizes.
Example and notes
A 100 kW load at 0.75 power factor has θ₁ = 41.4°, tan θ₁ = 0.882, and an apparent power of 133 kVA. To reach 0.95 (θ₂ = 18.2°, tan θ₂ = 0.329) you need Q = 100 × (0.882 − 0.329) ≈ 55 kVAR, which rounds up to a 60 kVAR standard bank and lands you a little above 0.95. Notice the apparent power drops from 133 kVA to about 105 kVA — that freed capacity is real and can defer a transformer upgrade. Avoid over-correcting: a leading power factor at light load raises voltage and risks resonance, and for direct motor correction stay within the manufacturer’s maximum kVAR to prevent self-excitation.