Why your LED lights flicker (and how to fix it)

Flickering LEDs almost always come down to one of a handful of causes, and most are a quick fix rather than a wiring fault. The usual culprit is a dimmer that was built for old incandescent globes and cannot cope with a low-wattage LED. Occasionally, though, flicker is a warning worth taking seriously.

This guide covers the common causes, how to tell them apart, how to fix each one, and the single pattern that means you should stop and call an electrician.

Find your flicker in one table

Match what you see to the likely cause. The sections below expand the ones worth explaining.

The usual cause: the wrong dimmer

Old dimmers were made for incandescent globes that draw 40 to 60 watts. An LED draws 5 to 10. Two things then go wrong: the dimmer expects a bigger load than the LED gives it, and it chops the mains waveform in a way (leading-edge) that LED drivers do not handle well. The result is flicker, flashing or a faint buzz, always worst at low brightness.

The fix is a trailing-edge dimmer, sometimes labelled ELV or LED compatible. It is built for low loads and switches the waveform in the way LED drivers handle cleanly. Check its rating covers the total watts of LED on the circuit.

Below the minimum load

Even a good LED dimmer has a minimum load, often around 10 watts. Put a single 5-watt bulb on it and there is too little for the dimmer to regulate, so it flickers or flashes instead of dimming. Add more bulbs to the circuit until you clear the minimum, or fit a dimmer rated to run a single low-wattage LED.

Cheap bulbs and the driver

Every LED runs off a small driver that smooths Australia's 240-volt, 50-hertz mains into steady power. A cheap driver does that job poorly, leaving a 100-hertz ripple you might see as a shimmer, or might not see at all. Invisible flicker still causes eye strain and headaches over a long evening. The test is simple: point your phone camera at the light. Rolling dark bands on the screen mean it is flickering faster than your eye can catch. Better-made LEDs from known brands flicker far less, because the driver is the part they do not skimp on.

When flicker is a warning, not a nuisance

Most flicker is harmless and fixable. Two patterns are not. If a whole circuit or several lights flicker together, at random, or the flickering is getting worse over time, that points to a loose connection or an overloaded circuit, and that is a fire risk. The same goes if you smell anything hot or see scorching at a switch or fitting. Turn it off and call a licensed electrician. In Australia, mains wiring is not a DIY job.

Smart bulbs: do not put them on a wall dimmer

A smart bulb dims itself electronically, over Wi-Fi, Zigbee or Bluetooth. Put one on a traditional wall dimmer and the two fight each other: the dimmer starves the bulb of the steady power it needs to run its radio and driver, and you get flicker or dropouts. Leave the wall dimmer or switch at full and dim in the app, or swap the dimmer for a smart dimmer designed to work with the bulbs. If you want a wall control, a smart switch or a wireless smart dimmer is the right tool, not an old triac dimmer.

Why your LED lights flicker: the short answer

Nine times out of ten it is the dimmer. Old dimmers were built for incandescent globes and cannot regulate a low-wattage LED, so fit a trailing-edge LED dimmer and make sure the bulb is marked dimmable. If bulbs shimmer even at full brightness, the driver is cheap, so switch to a known brand. And if a whole circuit flickers, randomly or worse over time, stop and call an electrician.