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Power Factor Correction Calculator: Capacitor kVAR
Estimate kvar needed to improve lagging power factor. Results include the values and assumptions used.
Formula and worked example
Qc = P × [tan(acos(PFpresent)) − tan(acos(PFtarget))]
S = P / PF; Q = P × tan(acos(PF)).
S = P / PF; Q = P × tan(acos(PF)).
How to use the calculation
P is active electrical power in kW, S is apparent power in kVA, Q is reactive power in kvar, and Qc is the theoretical capacitive compensation. Use comparable operating measurements and a target no lower than the present PF. This model assumes sinusoidal conditions and a lagging load.
Worked example
At 100 kW, improving PF from 0.80 to 0.95 needs approximately 42.1316 kvar theoretical compensation. Apparent power changes from 125 kVA to 105.2632 kVA in this calculation.
Common questions
Will this directly predict kWh savings?
No. Lower apparent/reactive power is not the same as lower real-energy consumption. Billing impact depends on your tariff and the installation.
Should I buy the next larger capacitor bank automatically?
Do not treat the theoretical kvar as an equipment selection. Bank steps, varying load, harmonics, switching and equipment instructions need separate design checks.
Can this calculate starting/run capacitors for a single-phase motor?
No. A motor starting/run capacitor has a different purpose and must follow the motor or manufacturer specification.
What happens when present and target PF are equal?
Required compensation is zero. This tool does not model correction of an already leading load.
Related electrical guides
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Formula references
Formula review: 31 October 2026. Examples are illustrative; use your actual equipment and project data.
