Power Factor Correction Calculator

How to use this calculator

1. Enter the real power of the load in kW.
2. Enter the existing power factor and the target power factor (e.g. 0.95).
3. Click Calculate to get the capacitor bank size in kVAR plus the kVA saving.

The formula

The reactive power that the correction capacitors must supply is the difference between the reactive power before and after correction:

Capacitor banks are rated in kVAR, so this is exactly the value you specify when ordering. Improving the power factor reduces the apparent power (kVA) and the current drawn, which can lower demand charges and free up transformer and cable capacity.

Why correct power factor?

A low power factor means a facility draws more current than the real power it uses, wasting capacity and often incurring utility penalties. Correcting it to 0.95 or higher is a common target for industrial sites.

Quick reference: kVAR per kW to reach 0.95

Multiply the figure by your real power in kW to get the capacitor bank size in kVAR.

Frequently asked questions

What is a good power factor?

0.95 or higher is a common target. Many utilities penalise customers whose power factor falls below about 0.9.

How many kVAR do I need to correct my power factor?

Use Qc = P × (tan(arccos PF1) − tan(arccos PF2)). For example, 100 kW from PF 0.8 to 0.95 needs about 42 kVAR.

What causes a low power factor?

Inductive loads such as motors, transformers and fluorescent ballasts draw reactive current that lowers the power factor.