If your electricity bill has "reactive power" or "availability" charges, or your supply feels full when the meter says otherwise, power factor is usually the reason.
The three kinds of power
Every AC installation deals with three related quantities:
The useful power that does work: turning motors, producing heat and light. This is what you'd think you're paying for.
Power that shuttles back and forth to magnetise motors and transformers. It does no useful work but still has to be delivered.
The total the supply must actually carry — the combination of real and reactive power. Your cables, transformer and DNO connection are all sized in kVA.
So what is power factor?
Power factor is simply the ratio of useful power to total power: kW ÷ kVA. A perfect score is 1.0. Most uncorrected commercial sites sit somewhere between 0.7 and 0.9. The lower the number, the more reactive power you're dragging through the system for no benefit.
What causes a poor power factor?
- Lightly loaded or oversized motors
- Transformers and welding equipment
- Older fluorescent lighting
- Induction heating and HVAC plant
The fix: power factor correction (PFC)
Power factor correction adds capacitance — usually an automatic capacitor bank — that supplies the reactive power locally, so the supply no longer has to carry it. Done well, PFC:
- Removes reactive-power and excess-kVA charges from the bill
- Frees up capacity on a supply that feels "full"
- Reduces losses and heating in cables and transformers
- Often pays back the install cost within one to three years
Find out what your power factor is costing you
A survey measures your true and displacement power factor and sizes the correction properly.
Book a power quality survey