Power Factor Correction Calculator
Capacitor kVAR and µF needed to raise PF to a target.
How to Use
- Enter load P (kW), current PF, target PF, voltage, frequency.
- Qc = P·(tan φ₁ − tan φ₂).
Show Work
Formulas
History of Power Factor Correction
Industrial capacitor banks for power-factor correction emerged in the 1910s as factories scaled up induction motor installations. Early banks used oil-filled paper capacitors rated at line voltage — bulky, expensive, and flammable if they failed. Mass adoption followed the 1920s-era spread of kVA-based utility tariffs, which financially punished factories for drawing reactive current they weren't paying for in kWh.
The mid-1960s brought a major shift with self-healing metallized polypropylene film capacitors, replacing oil-paper types. A small dielectric puncture vaporizes the metallized electrode locally, isolating the fault — so a single internal short no longer takes the unit out of service. Modern LV PFC banks at 480 V use these, typically arranged in switched steps of 25/50/100 kVAR controlled by a regulator that samples line current and adds steps as load PF drops.
Over-correction is a real hazard: leading power factor causes voltage rise on lightly-loaded feeders and — more dangerously — can resonate with transformer inductance at harmonic frequencies (5th, 7th, 11th) from nonlinear loads. This is why modern installations use detuned capacitor banks (with small series reactors) or active harmonic filters instead of raw capacitor banks on feeders with significant VFD/UPS loads.
About This Calculator
Enter the load's real power (kW), current PF, target PF, line-to-line voltage, and line frequency. The tool computes the required capacitor reactive power Qc = P·(tan φ₁ − tan φ₂), then the capacitance in both delta and wye configurations at line frequency. Delta needs one-third the capacitance of wye for the same kVAR because each capacitor sees full L-L voltage instead of L-N.
Practical notes: size to a target PF of 0.95–0.98, not unity — over-correction risks leading PF and resonance. Real installations use switched steps controlled by a PF regulator, detuning reactors in harmonic-rich environments, and discharge resistors on each step. This tool gives the ideal per-step rating; derate by 10–15% for harmonic current headroom. Everything runs client-side; no values leave your browser.
About the Power Factor Correction Calculator
Need a hand with electronics and circuit design? The Power Factor Correction Calculator does the work for you — free, and right here in your browser. Capacitor kVAR and µF needed to raise PF to a target.
How it works
Type your numbers into the boxes. The answer shows up right away — you do not have to press a button. If you change a number, the answer changes too. So you can try different numbers and watch what happens, or check an answer you worked out yourself. Just make sure each box has the right kind of number in it.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
Why correct?
Reduce kVA demand, utility penalties, and line losses.
Delta vs Wye cap?
Delta: C = Q/(3·ω·V_LL²). Wye: C = Q/(ω·V_LL²).
How do I use the Power Factor Correction Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
Factory Bank
Correct motor PF to 0.95.
Retail
Avoid demand penalty.
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