What is this?
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.
Common causes
- 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 to 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).
What will an electrician do?
Assess the current dimmer type and its compatibility with the installed bulbs
Replace the dimmer with an appropriate LED-compatible trailing-edge dimmer
Check and tighten all wiring connections at the switch
Ensure the total wattage meets the dimmer's minimum load requirement
Test the installation after replacement to confirm smooth, flicker-free dimming
Typical cost
£60 – £150
Dimmer switch replacement including a quality LED-compatible dimmer is typically £60–£100 for a single switch. Two-way dimmer setups cost more due to additional wiring.
