Electrical
Power Factor Correction
Capacitor kVAr needed to reach a target power factor — and the transformer and cable capacity that correcting it frees up.
Standard method — stated scope limits apply
Load
Enter load and power factors.
About This Calculation
A predominantly inductive industrial load (motors, transformers) draws reactive power (kVAR) in addition to real power (kW), which the supply and distribution system still has to carry even though it does no useful work — this shows up as a power factor below 1.0, higher apparent current for the same real power, and, in many tariff structures, a direct financial penalty. Power factor correction adds capacitor banks to supply reactive power locally, reducing the reactive current the utility supply and site cabling have to carry for the same real load.
Frequently Asked Questions
Why does poor power factor cost money even though the "wasted" power isn’t actually consumed?
Reactive current still flows through transformers, cables, and switchgear, requiring them to be sized larger than the real power alone would need — many utilities bill for this directly (a power factor penalty or kVA-based demand charge) precisely because it consumes real distribution system capacity even though it doesn’t register as consumed energy.
How much capacitance (kVAR) do I actually need to reach a target power factor?
The required kVAR is the difference between the reactive power at the current power factor and the reactive power that WOULD exist at the target power factor, for the same real power (kW) — both computed from kW × tan(θ), where θ is the phase angle corresponding to each power factor.
Can you overcorrect power factor, and is that a real problem?
Yes — too much capacitance makes the load net-capacitive (leading power factor), which can cause overvoltage at light load, resonance with system inductance (particularly a concern with harmonic-generating loads like VFDs), and some utilities penalize leading power factor just as they penalize lagging.
Where should capacitor banks physically be installed — centrally or at each motor?
Both are used in practice: individual (per-motor) correction avoids reactive current flowing through any of the site wiring at all, but is more capital-intensive per kVAR; central correction at the main switchboard is cheaper per kVAR but still leaves reactive current flowing through the branch circuits to each load. The right choice depends on which segment’s capacity is actually the constraint.