Power factor & harmonics, in plain language.
Two of the most common — and most fixable — drains on a commercial electricity account. Here's what they are, what they cost you, and exactly what correction looks like.
Paying for power that does no work.
Every AC installation deals with three kinds of power. Understanding them is the key to a lower bill.
Real power (kW)
The power that does useful work — turning motors, producing heat, driving production.
Reactive power (kVAr)
Power that shuttles back and forth to build the magnetic fields motors and transformers need. It does no useful work — but your cables and the utility still carry it.
Apparent power (kVA)
The total the supply must deliver. Power factor = kW ÷ kVA — a perfect site is 1.0; many industrial sites sit at 0.7–0.85.
What poor power factor costs you
- Higher kVA demand charges. SA commercial tariffs bill maximum demand in kVA — a poor power factor inflates it for the same real work.
- Reactive-energy penalties. A PF below ~0.90–0.96 is penalised — adding up to 25% to a bill.
- Wasted capacity. Reactive current fills cables and transformers — capacity you then pay to upgrade as you grow.
- Higher losses & voltage drop. More current means more I²R heating and sagging voltage across the plant.
The fix: power-factor correction
An automatic PF-correction (APFC) panel switches capacitor stages in and out to supply reactive power locally — holding your PF near target as load changes. Where harmonics are present, capacitors are detuned to avoid resonance.
Why distortion is expensive — and dangerous
- Overheated neutrals. Triplen harmonics add up in the neutral instead of cancelling — it can carry more current than the phases. A real fire risk.
- Transformer derating. Harmonic heating forces transformers below nameplate — you lose capacity you already paid for.
- Nuisance tripping & capacitor failure. Distorted waveforms trip protection and can drive capacitors into destructive resonance.
- Distortion power factor. Harmonics drag down your true PF — so penalties persist even after displacement correction.
The fix: harmonic mitigation
Sized from a logged survey: line reactors / DC chokes on drives, detuned capacitor banks, passive tuned filters, or — the premium, future-proof option — active harmonic filters (AHF) that inject an equal-and-opposite current to drive THDi below 5%.
The invisible distortion overheating your switchgear.
Your supply is a clean 50 Hz sine wave. Many modern loads are not.
A non-linear load — a variable-speed drive, UPS, LED driver, server power supply or EV charger — draws current in sharp pulses. Mathematically, that distorted current is the 50 Hz fundamental plus a series of higher-frequency harmonics (the 3rd at 150 Hz, 5th at 250 Hz, 7th at 350 Hz, and so on).
We measure the result as Total Harmonic Distortion (THD) — THDi for current, THDv for voltage. The international benchmark is IEEE 519, which Eskom references for connection limits (typically THDi ≤ 5%).
Watch the difference correction makes.
Toggle between an uncorrected and a corrected site. Drag the power-factor slider to explore — the diagrams, distortion and bill update live.
Power factor & demand
—Illustrative: 150 kW real load · R220/kVA demand charge.
Current waveform & THD
—Blue = measured current · cyan = ideal 50 Hz fundamental.
Want this analysis on your site?
We log it, correct it, and prove the return in a Power-to-Profit™ report.
Compliance isn't just regulatory — it pays.
A Certificate of Compliance is mandatory under SANS 10142-1. But the smartest clients treat it as a financial control, because the downside of getting it wrong dwarfs the cost of getting it right.
Insurance stays valid
If a fire or fault traces back to a non-compliant installation, insurers can repudiate the claim. One rejected claim can be hundreds of times the cost of the certificate.
Transactions complete
No valid CoC means a sale, transfer or lease can't legally close. A clean certificate keeps the deal — and your holding costs — moving.
The inspection finds the leaks
A proper inspection surfaces the same defects that quietly cost money — loose neutrals, poor earthing, low power factor. Every Apex CoC includes a free power-health snapshot.
Penalties & waste removed
Where the snapshot reveals a PF or harmonics issue, fixing it removes reactive penalties and releases supply capacity — often deferring a costly transformer upgrade.
Assets & uptime protected
Compliant, well-maintained installations fail less. Fewer unplanned outages, less equipment damage, longer asset life — straight to the bottom line.
Board-ready evidence
Paired with a Power-to-Profit™ report, compliance gives directors the audit trail and the numbers — NPV, IRR, payback — to sign off energy spend with confidence.
Compliance is the cheapest risk you'll ever retire.
A small, fixed, predictable cost that removes a large, uncertain, potentially catastrophic one — and frequently uncovers savings that pay for it many times over.