Nothing undermines confidence in an LED installation like flickering lights. I’ve had clients call in a panic weeks after a retrofit, convinced they’ve been sold defective products.

Sometimes they’re right. But often, the issue is power quality rather than product quality.

Let me explain what’s actually happening and how to diagnose it.

Why LEDs Can Flicker

Unlike incandescent lamps (which have thermal inertia that smooths fluctuations), LEDs respond almost instantly to changes in power supply. This makes them sensitive to electrical disturbances that older technologies largely ignored.

Common causes:

Driver Quality

The LED driver converts mains power to the DC voltage the LEDs need. Cheap drivers do this poorly, allowing AC ripple through to the LEDs. The result is visible flicker at mains frequency (100Hz in Australia—twice the 50Hz supply frequency).

Quality drivers have better filtering and produce smooth, stable output. This is why I keep banging on about driver brands: Philips Xitanium, Osram, Meanwell—these are reliable. No-name drivers are a gamble.

Dimmer Compatibility

LEDs on dimmers can flicker if the dimmer type doesn’t match the driver requirements.

Old incandescent dimmers (leading-edge/triac) often don’t work well with LED drivers. LED-compatible dimmers (usually trailing-edge) are needed.

Even with compatible dimmers, there’s a minimum load issue. A dimmer designed for 200W of incandescent lamps might behave erratically with 30W of LEDs.

Solution: Use dimmers specifically rated for LED loads. Check manufacturer compatibility lists. Some LED fittings need specific dimmer models.

Voltage Fluctuations

If your supply voltage varies, LEDs respond visibly. Common causes:

• Heavy loads switching nearby (motors, HVAC, welders)
• Poor supply quality from the distribution network
• Voltage drop on long cable runs

A voltage fluctuation that’s imperceptible with fluorescents might be obvious with LEDs.

Harmonic Distortion

Modern facilities have lots of electronic loads: computers, variable speed drives, other LED lighting. These create harmonic distortion on the supply. In severe cases, this affects LED performance.

Loose Connections

Simple but often overlooked. A connection that’s slightly loose can cause intermittent contact, which shows up as flicker. Check terminations.

Diagnosing the Problem

Step 1: Isolate the Scope

Is it one fitting, a group, or everything?

• Single fitting: Likely a fitting or driver fault
• Group on same circuit: Likely circuit issue (dimmer, wiring, breaker)
• Everything: Likely supply issue or systemic problem

Step 2: Timing Pattern

When does the flicker occur?

• Constant, rhythmic flicker: Driver issue (100Hz flicker) or dimmer compatibility
• Random, intermittent flicker: Voltage fluctuations, loose connections, or interference
• Correlates with other equipment: Load switching affecting supply

Step 3: Power Quality Measurement

For persistent issues, measure the supply:

• Voltage level (should be 230V ±10% in Australia)
• Voltage fluctuations (rapid variations)
• Total harmonic distortion (THD)
• Frequency (should be stable at 50Hz)

A power quality analyser can reveal problems invisible to basic meters. If you suspect supply issues, this is worth the investment or hire.

Step 4: Test Components

Try swapping components to isolate the problem:

• Replace the suspect fitting with a known-good unit
• Bypass the dimmer (connect direct to mains)
• Test on a different circuit

Systematic isolation usually finds the cause.

Common Scenarios and Solutions

Scenario 1: Flicker on All Fittings on One Dimmer Circuit

Likely cause: Dimmer incompatibility or minimum load issue.

Solution: Replace the dimmer with an LED-compatible model. If the total LED load is very low, some electricians add a “minimum load module” to satisfy the dimmer’s requirements.

Scenario 2: Random Flicker Correlating with AC System

Likely cause: Compressor start/stop causing voltage sag.

Solution: Power quality investigation. Possible solutions include power factor correction, soft starters on motors, or supply upgrades. This can be complex and expensive—weigh up whether it’s worth fixing or whether you can live with it.

Scenario 3: One Fitting Flickers Constantly

Likely cause: Faulty driver or LED module.

Solution: Replace under warranty if applicable. If out of warranty, replace the fitting.

Scenario 4: Flicker Visible Only on Camera

Phone cameras and video equipment can reveal flicker that’s invisible to the eye (due to camera frame rates interacting with light frequencies).

This isn’t necessarily a problem for human occupants but can be problematic for photography, video production, or retail environments where customers take photos.

Solution: High-frequency drivers (>1000Hz switching frequency) or flicker-free rated products.

Prevention at Specification Stage

The best cure is prevention. When specifying LEDs:

Require quality drivers: Specify driver brands or insist on flicker-free certifications (IEEE PAR 1789 is a relevant standard for biological effects of light flicker).

Consider the application: Video and broadcast environments need very low flicker. Warehouses can tolerate more.

Match dimmers properly: If dimming is required, specify compatible dimmer models at the same time as fittings.

Check the electrical infrastructure: If you know there are power quality issues on site, address them first or specify fittings designed to tolerate poor supply.

When to Call for Help

Some flicker issues are straightforward. Others get complicated.

If you’ve done basic troubleshooting and can’t find the cause, it might be time for:

• A power quality specialist
• The fitting manufacturer’s technical support
• A lighting consultant who’s seen similar issues

Don’t keep replacing fittings hoping the problem goes away. Diagnose properly, then fix.

The Broader Picture

LED flicker has received increasing attention as LED adoption has grown. Standards are evolving, and quality products are genuinely better than a few years ago.

But the market still has cheap products with poor electrical performance. The price for avoiding flicker problems is specifying quality in the first place.

It’s usually cheaper to do it right initially than to troubleshoot problems after installation.