Why do my lights flicker?

Which flickers are a cheap bulb problem and which mean a loose connection that needs an electrician.

Difficulty: beginner
Time: 20 min
Read: 3 min
Safety: warning

Short answer

One light flickering is usually the bulb or the fitting. Several lights or the whole house flickering suggests a supply or connection problem, and that is an electrician's job rather than a bulb change.

Flickering ranges from a mildly annoying LED to a genuine warning sign, and the difference is mostly about how much of the house is affected. That single distinction tells you whether to buy a bulb or make a call.

Safety

Flickering across the whole house, flickering with a burning smell, warm switches or sockets, or lights dimming when an appliance starts are all reasons to call a qualified electrician promptly. A loose connection is a genuine fire risk. Do not investigate inside a consumer unit or open any accessory yourself.

Step by step

Work out how much is affected.One fitting, one circuit, or the whole house. This is the most informative thing you can establish and it takes a minute.
For one light: change the bulb.The cheapest test. Cheap LEDs flicker as they fail, and a bulb that is not fully seated in the fitting flickers intermittently.
Check dimmer compatibility.By far the most common cause of LED flicker. Many LEDs need a dimmer designed for them, and an old dimmer made for filament bulbs will flicker or buzz with LEDs.
Note whether it flickers when something starts up.Lights dipping briefly when the fridge, shower or washing machine starts can be normal on a heavily loaded supply, but if it is pronounced or new it should be checked.
Check whether it is worse in bad weather.Flickering during wind or rain suggests a problem with the incoming supply rather than your wiring. Report it to the network operator, not an electrician — that is their equipment and their responsibility.
Treat whole-house flicker as urgent.Every light flickering, or flickering with any smell, warmth or buzzing, points at a loose connection. That generates heat and it is a fire risk.
Do not investigate inside the consumer unit.This is exactly the boundary. Even competent DIY stops here — it is notifiable work and it is where the danger is.
Book an electrician for anything beyond a bulb.Describe what you observed: how many lights, when, whether anything else was running, whether it correlates with weather. It shortens the visit considerably.

Tips

Very cheap LED bulbs flicker more as they age, and some flicker at a frequency people notice as eye strain without registering it as flicker.
Note the pattern before calling — constant, intermittent, on start-up, weather-related. It is the first thing you will be asked.
If lights flicker only on one circuit, say so. It narrows the fault to a specific part of the installation immediately.

If it doesn't work

One LED bulb flickers

Cause: Failing bulb, loose fitting, or incompatible dimmer — Fix: Change the bulb, check it is seated, and confirm the dimmer is LED-compatible.

Lights dip when an appliance starts

Cause: Normal load on the supply, or an undersized circuit — Fix: Occasional and slight is usually fine. Pronounced or new should be checked by an electrician.

Whole house flickers

Cause: Loose connection or supply fault — Fix: Electrician promptly. If it correlates with weather, report to the network operator first.

Flicker with buzzing, warmth or smell

Cause: Loose connection generating heat — Fix: Turn that circuit off if you safely can and call an electrician immediately. This is a fire risk.

Questions people ask

Is a flickering light dangerous?

One bulb, usually not. Several lights or the whole house can indicate a loose connection, which generates heat and is a genuine fire risk — that needs an electrician promptly.

Why do my LED bulbs flicker on a dimmer?

Most likely the dimmer was made for filament bulbs. LEDs need a compatible dimmer, and mismatches cause flickering and buzzing.