Power Surges and Flickering Lights: Causes and What to Do
Lights that pulse brighter and dimmer, flicker when an appliance starts, or surge for no obvious reason are more than an annoyance. Sometimes the cause is harmless. Sometimes it is a loose connection that can overheat. Here is how to tell the difference.
Common causes
1. A big appliance starting up
A brief dip in the lights when a fridge compressor, washing machine or electric shower switches on is common and usually harmless. The motor draws a surge of current as it starts. If the dimming is severe or happens with small appliances, something is wrong.
2. A loose connection
A loose wire at a light fitting, switch, socket or in the consumer unit causes flickering and surging, and it can arc and overheat. This is one of the most important causes to take seriously, particularly if you notice a burning smell, buzzing or warm fittings.
3. A loose or faulty neutral
If the neutral connection fails, voltage in the house can swing up and down. Lights may go very bright, then dim, and appliances can be damaged. This is dangerous and needs an electrician urgently. It can occur in your wiring or in the supply to your property.
4. Overloaded circuits
Too many high-power items on one circuit can cause lights to dim and the breaker to trip. See our guide on why a fuse box keeps tripping.
5. Incompatible dimmers or LED bulbs
Flickering LEDs are often caused by an old dimmer switch that is not designed for LED loads, or by cheap bulbs. Changing the bulb or fitting an LED-compatible dimmer usually fixes it.
6. Problems with the supply
If the whole street sees flickering or surges, the fault may be on the network. Call 105 to report it to your distribution network operator.
7. Lightning and external surges
A strike nearby can send a spike through the supply and damage electronics. Whole-home surge protection devices fitted at the consumer unit can reduce the risk.
What you can check safely
- Does it affect one light, one room or the whole house?
- Does it happen when a particular appliance starts?
- Try a different bulb in the affected fitting.
- Check whether neighbours have the same problem.
When to call an electrician urgently
- Lights go very bright, then dim, across several rooms
- A burning smell, buzzing, crackling or warm fittings
- Appliances are failing or electronics are being damaged
- The flickering is getting worse
Switch off the affected circuit or the main switch if you are concerned, and do not keep using it. Our team can trace the fault; see our burning smell and fuse box tripping pages for related problems.
Seeing surges or flickering? Call 020 3411 2027 and we will help you find out whether it is harmless or urgent.
