How to protect electronics from a power surge, including after a power cut

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The surest way to protect electronics from a power surge in a power cut is to turn them off or unplug them until the power is back. Ready.gov says power can return with momentary surges or spikes that cause damage. A surge protector helps with the surges a power cut can bring, but typical ones won't protect against a lightning strike.

Quick answer

When the power goes off, turn off or unplug computers, TVs, laptops, tablets and phones, and leave one light on so you know when it returns. Protect sensitive equipment with a surge protector plug or an uninterruptible power supply. Typical surge protectors won't stop a lightning strike, and you shouldn't unplug anything during a thunderstorm.

Why can a power cut damage electronics?

The risk is the moment the power comes back. Ready.gov, the US government's preparedness site, says power may return with momentary surges or spikes that can cause damage. In the UK, National Grid says electrical surges during power cuts can damage digital devices such as phones, TVs, laptops and tablets.

Lightning causes surges too. The US National Weather Service says lightning generates electric surges that can damage electronic equipment some distance from the strike, and that lightning can travel through a building's electrical, phone, plumbing and radio and TV reception systems.

Should I unplug everything during a power cut?

Turn off or unplug sensitive equipment. UK and US advice agree on this.

UK: National Grid's tips are to turn off and unplug any sensitive equipment, such as TVs and computers, and to turn off and unplug appliances that get hot, because you may forget they're switched on when the power returns.

US: Ready.gov says to turn off or disconnect appliances, equipment and electronics, to avoid damage from electrical surges.

  1. Turn off and unplug computers, TVs, laptops, tablets and phones.
  2. Turn off and unplug appliances that get hot.
  3. Leave one light switched on. National Grid suggests this so you know when the power is back.

If your Mac won't start afterwards, our guide to a Mac after a power cut has Apple's steps.

Do surge protectors work?

For the surges that can come with a power cut, National Grid's advice is to use one. National Grid says to protect sensitive and valuable electrical equipment with a surge protector, which guards against damage from sudden surges that can happen during a power cut. Its power cut leaflet suggests a surge protector plug or an uninterruptible power supply (UPS) for sensitive equipment such as computers or medical equipment.

Ready.gov also suggests considering surge protectors, lightning rods or a lightning protection system to protect your home, appliances and electronic devices from thunderstorms.

There's a limit. The National Weather Service says typical surge protectors will not protect equipment from a lightning strike.

How do I protect electronics in a thunderstorm?

Not by unplugging things while the storm is overhead.

US: the National Weather Service says not to unplug equipment during a thunderstorm, because there's a risk you could be struck. It also says not to touch electrical equipment such as computers, TVs or cords, and to stay off corded phones. You can use mobile or cordless phones. Ready.gov says to avoid using electronic devices connected to an electrical outlet during a storm.

UK: if a storm cuts your power, National Grid's power cut advice above applies.

How do I use a surge protection extension lead safely?

A surge protection extension lead is still an extension lead, and the usual safety rules apply.

UK: Electrical Safety First, the UK electrical safety charity, says:

  1. Check the rating before you use it. Most extension leads are rated at 13A, but some older ones and many cable reels may be 10A or less. Overloading a lead can make it, or the plug in the wall socket, overheat and cause a fire. Its online socket overload calculator helps you check.
  2. Use only one extension lead per socket, and never plug an extension lead into another one.
  3. Buy from a reputable retailer rather than a third-party seller online, and make sure it has a standard UK 3-pin plug and a fuse.
  4. Register the product, so the maker can contact you if there's a safety recall.

US: the Consumer Product Safety Commission (CPSC) says to look for a certification mark from an independent testing laboratory, and to check the underside of a power strip or surge protector for the manufacturer's name and the testing lab. It also advises using power strips and surge protectors with polarised or grounded three-pronged plugs, not overloading cords, never covering a cord in use with a rug, and throwing away any cord that feels hot to the touch.

My surge protector stopped working after a surge. What now?

Electrical Safety First says the surge protection parts in extension leads, called MOVs, are generally self-resetting. If the lead doesn't work after a surge, the fuse protecting that part may have blown.

  1. If the lead has a replaceable fuse, try changing it, or change the fuse in its plug.
  2. If that doesn't work, replace the extension lead.

Watch for warning signs on any lead or socket. Electrical Safety First lists a smell of hot plastic or burning, sparks or smoke, scorch marks, damaged or frayed cables, melted plastic, and fuses that blow or circuit breakers that trip for no obvious reason. If you see any of these, unplug the product and contact the retailer, the manufacturer or a qualified repair technician.

More questions

Can a power cut damage my computer?

The return of power can. Ready.gov says power may come back with momentary surges or spikes that can cause damage, and National Grid says surges during power cuts can damage laptops, phones, TVs and tablets. Turn them off or unplug them until the power is back.

Does a surge protector protect against lightning?

Not from a strike. The US National Weather Service says typical surge protectors will not protect equipment from a lightning strike. Ready.gov suggests considering surge protectors, lightning rods or a lightning protection system for your home, and avoiding devices connected to an outlet during a storm.

Should I unplug my TV during a thunderstorm?

No. The US National Weather Service says not to unplug equipment during a thunderstorm, because there's a risk you could be struck, and not to touch electrical equipment such as computers, TVs or cords. Ready.gov says to avoid using devices connected to an outlet during a storm.

What is a UPS?

An uninterruptible power supply. National Grid's power cut leaflet suggests protecting sensitive equipment, such as computers or medical equipment, with a surge protector plug or a UPS. It also says to make sure any medical equipment has a battery back-up for a power cut.

Can I plug a surge protector into an extension lead?

No. Electrical Safety First says to use only one extension lead per socket and never to plug one extension lead into another, known as daisy chaining. It says this risks overloading the wall socket. Move the appliance closer to the wall socket instead.

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