Why do my lights flicker on a dimmer switch?

The most common cause is using an old-style leading-edge dimmer with LED bulbs. LEDs draw very little power and standard dimmers cannot regulate them properly, causing flickering. You need an LED-compatible trailing-edge dimmer.

What is the difference between leading-edge and trailing-edge dimmers?

Leading-edge dimmers were designed for incandescent and halogen bulbs at higher wattages. Trailing-edge dimmers are designed for the much lower loads of LED bulbs and provide smooth, flicker-free dimming.

Can I mix LED and halogen bulbs on the same dimmer?

It is not recommended. Different bulb types respond differently to dimming, which can cause flickering and uneven brightness. Use all the same type and ideally the same brand and model.

My dimmer has a minimum load — what does that mean?

Dimmers need a minimum wattage to work correctly. If your LED bulbs total less than the dimmer's minimum load (often 25W–40W), the dimmer cannot regulate the current and the lights will flicker. An LED dimmer has a much lower minimum load.

Is it worth getting a branded dimmer switch?

Yes. Quality dimmers from brands like Varilight, Hamilton, and BG Electrical are specifically designed for LED compatibility and offer smooth dimming without flicker. They are not significantly more expensive than budget options.

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Updated 30 August 2026

Dimmer Lights Flickering

Lights on a dimmer switch are flickering, strobing, or not dimming smoothly.

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What's happening?

Flickering on a dimmer-controlled circuit is the most common dimmer complaint in UK homes, especially since the switch to LED lighting. Dimmers regulate brightness by rapidly switching the power on and off. If the dimmer and bulb are not compatible, or the dimmer is overloaded or underloaded, the lights will flicker, strobe, or behave erratically.

What usually causes it?

Leading-edge (triac) dimmer being used with LED bulbs — the most common cause
LED bulbs that are not rated as dimmable
Total wattage of LEDs is below the dimmer's minimum load requirement
Dimmer switch is old, worn, or has corroded contacts
Mixed bulb types on the same dimmer (e.g., LED and halogen together)
Loose wiring connections at the dimmer switch

Is it dangerous?

Dimmer-related flickering is usually a compatibility issue rather than a safety hazard. However, an old dimmer running very hot to the touch, or one that buzzes loudly, should be replaced. Cheap or faulty dimmers can overheat, which is a fire risk, especially when fitted in a plastic back box in a plasterboard wall.

Can I fix it myself?

The most effective DIY fix is ensuring your bulbs are dimmable LEDs from a reputable brand and that all bulbs on the dimmer are the same type and wattage. If you have a standard (leading-edge) dimmer, it likely needs replacing with an LED-compatible trailing-edge dimmer. Dimmer replacement is a common DIY task but requires isolating the circuit at the consumer unit and some electrical competence.

When should you call an electrician?

Call an electrician if you are not confident replacing a dimmer switch yourself, if the dimmer feels hot or buzzes loudly, if the flickering persists after replacing the dimmer and bulbs, or if the dimmer is on a two-way or intermediate switching circuit (more complex wiring).