APFC panel — what it is, how it works, and how to size it

Automation & IoT · 7 min read · Updated 2026-04-21
TL;DR

APFC = Automatic Power Factor Correction. It switches capacitor steps ON/OFF to keep PF near 0.95–0.99. In kVAh-based tariffs, it reduces billed units and demand by lowering kVA.

APFC panel basics

An APFC panel continuously measures PF and switches capacitor steps to compensate reactive power. This reduces current, transformer loading, and kVA-based charges.

What’s inside an APFC panel?

  • —APFC controller (PF sensing + step logic)
  • —Capacitor steps (kVAr)
  • —Contactors/thyristor switching
  • —Detuned reactors (recommended with harmonics/VFDs)
  • —Protection: fuses, MCB/MCCB, temperature monitoring

Sizing rule of thumb

Sizing depends on your kW load and present PF vs target PF. An energy audit or incomer meter data makes the sizing accurate and avoids over-compensation.

Frequently asked questions

Can APFC increase my bill?

If poorly sized, it can cause leading PF or resonance with harmonics. Using detuned reactors and data-based sizing prevents this.

Do I need APFC if I have solar?

Solar doesn’t automatically fix PF. Many inverters operate near unity PF but your inductive loads still affect overall PF.

How do I confirm APFC savings?

Track PF and kVAh/kWh gap before and after using a three-phase meter and your tariff’s penalty/rebate terms.

Related from Enlog

Power factor correction basicskVAh formula articleEnPro PF & kVAh metering

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