What is this?
A power surge is a sudden spike in voltage that exceeds the normal 230V mains supply. Surges can last microseconds but carry enough energy to damage or destroy electronic equipment, appliances, and even wiring insulation. They can be caused by lightning, faults on the electricity network, large appliances switching on and off, or supply restoration after a power cut.
Common causes
- Lightning strike on or near the local electricity network
- Fault on the Distribution Network Operator's supply infrastructure
- Power restoration after a power cut causing a transient spike
- Large motors or compressors (industrial or domestic) switching on
- Switching operations on the national grid
Is it dangerous?
Power surge damage itself is not an ongoing danger if the protective devices have operated correctly. However, surges can cause hidden damage to wiring insulation that degrades over time and creates fire risks. If your consumer unit or wiring shows any signs of damage (scorch marks, burning smell), treat it as an emergency.
Can I fix it myself?
Check your consumer unit for tripped MCBs or RCDs and reset them. Test appliances one at a time. Unplug and do not use any appliance that smells burnt, makes unusual noises, or appears damaged. Check sensitive electronics (computers, TVs, routers) for damage. You can replace obviously failed items, but the installation itself should be checked professionally if you suspect significant surge damage.
When to call an electrician
Call an electrician if multiple appliances have been damaged (suggesting a significant surge), if the consumer unit shows signs of damage, if MCBs or RCDs will not reset after the surge, or if you want surge protection devices fitted to prevent future damage.
What will an electrician do?
Test the consumer unit and all protective devices for surge damage
Check wiring insulation resistance on all circuits
Replace any damaged MCBs, RCDs, or the consumer unit itself
Install Type 1 and/or Type 2 surge protection devices (SPDs)
Advise on protecting sensitive equipment with point-of-use surge protectors
Typical cost
£150 – £500
Inspection and repair after a surge event. Surge protection device (SPD) installation in the consumer unit costs £150–£300. Consumer unit replacement if needed is £350–£600.
