Protecting appliances from surges when the power returns
What damages your appliances during an outage is usually not the power going off — it is the power coming back. When supply is restored, there can be a brief rise in voltage, and that is what wears down sensitive electronics over the years or kills them outright in one go.
Why the return is the risky part
When an outage ends, every house on that line is energised at the same moment. For a few seconds, the load and the voltage on the network may not have settled.
Add to that everything you left switched on during the outage, all starting at once. Air conditioners, fridge compressors, water pumps and heaters draw far more current at start-up than they do running. Every one of those on a street kicking in within the same second contributes to the swing.
The risk is higher after a fault than after planned work, because the network was interrupted by a failure rather than by an orderly shutdown.
What to do when the outage starts
The most effective protection is the simplest, and it costs nothing: unplug the things you care about.
Roughly in order of priority:
- Computers, monitors, external drives
- TV, sound system, games console
- Modem and router
- Chargers and power adapters
- White goods with electronic controls — oven, microwave, dishwasher
The fridge and freezer are usually better left plugged in, since they need to start cooling again as soon as the power returns. If what is inside matters more to you than the appliance, leave them connected.
Turning an air conditioner off with the remote is not enough — many models just go to standby. Switch it off at the wall or at its breaker.
Whatever you do leave plugged in, at least leave it switched off, so it is not one more thing starting up at the same instant as everything else.
After the power comes back
When you notice the power is back, do not plug everything in straight away.
Wait a few minutes. That is long enough for the voltage to settle, and it costs you nothing.
Plug things in one at a time. One device, then the next. Switching everything on together is exactly the sudden load you were trying to avoid.
If the power is flickering on and off, plug in nothing. Crews may still be working on the line. That unsettled period is riskier than a steady outage. Wait until it holds.
If something does not work after the power returns, check its fuse at the consumer unit and the appliance's own fuse before taking it for repair.
Surge protectors
A surge-protected socket strip absorbs part of a voltage spike. It is a sensible thing to own for the times you do not get to unplug.
Its limits are worth knowing.
An ordinary extension lead does not protect against surges. If it does not explicitly say "surge protection" or give a joule rating, it is just a socket strip.
Surge protectors wear out. The protective component inside degrades a little with every spike it absorbs, and one day it stops protecting — usually without telling you. Prefer models with a status light, and replace them every few years.
A surge protector will not save equipment from a lightning strike. For a direct strike, the only reliable protection is being unplugged.
Uninterruptible power supplies
A UPS both protects against surges and runs from its battery for a few minutes when the power goes. Those few minutes are enough to shut a desktop computer down properly, which saves both your work and your drive.
For a home, a UPS makes sense for a few critical things like a computer and the modem. A domestic UPS is not suitable for high-power appliances such as a fridge or an air conditioner.
When it keeps happening
If bulbs in the same house fail often, appliances break for no obvious reason, or the lights flicker noticeably as the power returns, the problem may be with the installation rather than with individual devices.
Have an electrician check the wiring and the earthing. If the problem is on the network side, report it to your regional office — the numbers are in our fault reporting guide.