LED lighting saves energy. Everyone knows that. What fewer people understand is that LED drivers can create electrical disturbances that cause problems elsewhere in your building.

I’ve been called to troubleshoot several facilities where the LED retrofit went well—until other equipment started misbehaving.

What Are Harmonics?

Your electricity supply is meant to be a clean 50Hz sine wave. In reality, it’s never perfect.

Non-linear loads—anything with electronic power conversion—distort the waveform. Instead of a smooth sine wave, you get additional frequency components layered on top: 150Hz, 250Hz, 350Hz, and so on. These are harmonics.

Every LED driver contains power electronics that create harmonics. The question is how much and whether it matters.

Why This Became an Issue

In the old days of magnetic fluorescent ballasts, harmonics were minimal. Ballasts were basically inductive loads—they shifted the current phase but didn’t distort the waveform much.

LED drivers are different. They rectify AC to DC, smooth it with capacitors, and regulate output for the LEDs. This process draws current in pulses rather than smoothly, creating harmonic distortion.

When you had a few LED fittings, the harmonics were negligible. When you retrofit an entire building to LED, suddenly a significant portion of your total load is creating harmonics. The effect compounds.

The Real-World Problems

Here’s what harmonic distortion can cause:

Neutral conductor overheating: In a three-phase system, balanced loads should cancel in the neutral. But triplen harmonics (3rd, 9th, 15th) add up rather than cancelling. A neutral conductor sized for normal loads can overheat.

Transformer overheating: Transformers are designed for 50Hz. Higher frequencies create additional losses. A transformer running LED-heavy loads may run hotter than expected.

Electronic equipment malfunction: Sensitive equipment—computers, servers, medical devices, instrumentation—can behave unpredictably with distorted supply.

Nuisance circuit breaker tripping: Some circuit breakers trip on peak current, which is higher with distorted waveforms.

Interference: Radio frequency interference can affect communications equipment.

Measuring the Problem

You can’t see harmonics. You need to measure them.

Power quality analyser: The proper tool. Records voltage and current waveforms, calculates THD (Total Harmonic Distortion), identifies which harmonics are present.

What to look for:

• THD voltage over 5% is concerning for sensitive loads
• THD current over 20% on the neutral warrants investigation
• 3rd harmonic dominant is typical of LED/electronic loads

When to measure: After a major LED retrofit. When electrical problems emerge. Before planning additional electronic loads.

What the Standards Say

AS/NZS 61000.3.2 sets limits for harmonic current emissions from individual equipment under 16A. Reputable LED products should comply.

EN 61000-3-2 is the European equivalent, often referenced on Australian product data sheets.

But here’s the catch: individual products can comply while the aggregate effect of many products causes problems. Standards limit what each device does; they don’t guarantee system-level outcomes.

Choosing Better Products

Not all LED drivers create equal harmonics. Quality matters.

What to look for in specifications:

• Power Factor (PF) close to 1.0 (0.95+ is good)
• THD current specified (under 15% is good, under 10% is better)
• Compliance with IEC 61000-3-2

What happens with cheap products:

• PF of 0.7-0.8 (acceptable for compliance but worse for harmonics)
• Higher THD (sometimes 30%+)
• No harmonic data published (suspicious)

The price difference between a 0.95 PF driver and a 0.7 PF driver might be $5-10 per fitting. Over hundreds of fittings, that adds up. But so do power quality problems.

Solutions for Existing Problems

If you’ve got harmonic issues after an LED retrofit, options include:

Verify the problem: Get a proper power quality assessment before spending money on solutions.

Upgrade neutral conductors: If neutral overloading is the issue, larger neutrals may be the answer. Not cheap if they’re buried in walls.

Add harmonic filters: Passive or active filters can reduce harmonic content. These are additional equipment with ongoing maintenance.

Replace problematic drivers: Sometimes the cheapest solution is replacing the worst offending fittings with better quality ones.

Separate sensitive loads: Put critical equipment on dedicated circuits or UPS with clean output.

Derate equipment: Transformers and cables may need to carry less load to accommodate the additional heating.

Prevention Is Better

For new LED projects:

Specify quality: Include PF and THD requirements in specifications. Accept a modest cost premium for better electrical characteristics.

Diversity helps: Different LED products from different manufacturers have different harmonic profiles. A mix tends to create less resonance than identical products throughout.

Consider the electrical infrastructure: Is the neutral conductor sized for potential harmonic currents? Is the transformer rated for non-linear loads?

Plan for measurement: Budget for a post-installation power quality assessment to confirm acceptable conditions.

When to Involve Specialists

Basic harmonic awareness is part of every commercial electrician’s knowledge. But complex power quality problems may need specialist help.

Call in experts when:

• Power quality measurements show unexplained distortion
• Equipment is malfunctioning despite adequate supply
• You’re planning major electronic load additions to an already loaded installation
• Proposed solutions are expensive and you want confidence they’ll work

Power quality consultants with appropriate test equipment can diagnose problems and model solutions. This is different from lighting specialists or general electrical contractors—it’s a specific discipline.

For buildings with sophisticated energy management and automation systems, the integration specialists handling that work—companies like Team400 who focus on intelligent building technology—often work alongside power quality consultants to ensure the building’s electrical infrastructure supports its smart systems.

My Experience

Most LED retrofits don’t cause significant harmonic problems. Modern quality drivers are reasonably well-behaved. The issues arise when:

• Very large LED loads on relatively small electrical systems
• Cheap products with poor power factor
• Pre-existing marginal conditions worsened by the retrofit
• Sensitive equipment on shared circuits

The prevention cost is small (specify quality products, verify after installation). The remediation cost is larger (filters, rewiring, specialist consultants).

Like many things in this industry, doing it right the first time is cheaper than fixing problems later.

Key Takeaways

1. LED retrofits change your electrical load characteristics, not just the magnitude
2. Quality LED drivers with high power factor and low THD reduce problems
3. Large LED installations deserve post-installation power quality checks
4. Neutral conductors may need reassessment for LED-heavy buildings
5. Problems are easier to prevent than to solve after installation

Don’t let power quality issues undermine the benefits of your LED retrofit. Understand the risk, specify appropriately, and verify the outcome.

James Thornton has been working in commercial lighting for 18 years and is based in Australia.