Power factor correction calculator (kvar)
Useful for plants and buildings that pay a low power factor penalty or want to ease the load on a transformer.
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How to use it
- Enter real power, present power factor and target power factor.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Qc = P × (tan φ1 − tan φ2), where φ = arccos(PF). Apparent power S = P ÷ PF, and current reduction = 1 − PF1 ÷ PF2.
Example
Inputs: Real power = 100 kW, Present power factor = 0.7, Target power factor = 0.95. Result: Capacitor rating needed: 69.15 kvar; Apparent power before: 142.86 kVA; Apparent power after: 105.26 kVA.
Limits and caveats
- The result is total capacitor kvar; capacitance in µF depends on voltage, frequency and star or delta connection.
- Harmonics are not included; with many non-linear loads the capacitors may need detuning reactors.
- The penalty threshold and required power factor are set by your utility.
Questions about this tool
Why not correct all the way to 1?
The last step needs a lot of capacitance for little gain and can cause overvoltage at light load. Common targets are 0.95 to 0.98.
How many kvar for 100 kW from 0.7 to 0.95?
About 69.2 kvar, and apparent load falls from 142.9 to 105.3 kVA.
Does power factor correction reduce kWh?
It does not change the real power the equipment uses, but it cuts current and cable losses and may remove a reactive power penalty.