How to avoid overloading your plug sockets at home

Overloading your plug sockets with multiple electric appliances can be tempting, but just because your extension lead can squeeze in four plugs doesn't mean it's safe to do so.

Some appliances require so much power that, when grouped together, they can cause the plug to overheat and possibly start a fire.

To help you stay safe, we've listed the most energy-guzzling appliances below to help you understand what devices - when used in tandem - might overload your sockets.

We also look at whether it's safe to leave your phone or laptop charging overnight.

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How much power do your appliances need?

Surprisingly, some of the smallest appliances in our homes use the most watts of power.

In fact, a typical kettle uses around 3,000 watts - significantly more power than a fridge, even though the kettle will only be active for short durations. And an iron can use up to 720 times more power during operation than is needed for a mobile phone charger.

As a guide, you should only load one plug socket with a maximum of 3,000 watts. But it might be easier to remember the sorts of products that require more and less around the home. 

If you're not sure which appliance works with which, then take a look this handy socket calculator.

Are overloaded plug sockets a fire hazard?

We asked Tim Benham, technical support officer from Royal Berkshire Fire and Rescue, how many plugs are too many when plugging devices into an outlet.

He said: 'It really depends on the appliances you're plugging in. Always work out the total wattage of all the devices going into the one socket.

'If they add up to more than 3,000W then it's not safe - the plug in the socket can overheat and potentially cause a fire.'

Here are four examples of what not to pair up using an extension lead. 

High-powered appliances, such as kettles, washing machines, or dishwashers, can easily overload an adaptor or extension lead, posing a safety risk, no matter how energy efficient the appliance might be.

'A kettle can max out the socket capacity all on its own, while having your washing machine and dishwasher plugged into an adaptor would mean you're a massive 1,440 watts over the recommended amount,' he said.

'Appliances like your fridge, radio or lamp are far more suited to sharing sockets. Take note if you're moving plugs around to try to squeeze extra devices in.'

Is it safer to pair appliances alongside each other in a twin-outlet plug?

'While each socket usually in a twin-outlet plug is rated to 13 amps and, in theory should be able to handle that load, we wouldn't advise doing this,' said Mr Benham.

'If you suspect one plug in a twin-outlet socket is heavily loaded, try to only use low-power devices in the other one, just to be on the safe side, or use a different socket.'

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And is it really a bad idea to connect one extension lead to another one?

'Yes it is,' he said. 'You should never "daisy-chain" extension leads together. If you use more than one extension lead per socket it will significantly raise the risk of overloading the socket.'

While safety comes first, energy efficiency is also vital for managing household bills and reducing environmental impact.

Our independent reviews test appliances for energy efficiency, so you can understand annual running costs before you buy. Explore our guides to the most energy efficient washing machines, energy efficient fridges and energy efficient dishwashers to help you make informed choices for your home.

Good smoke detectors warn you early when there's a real fire and give you time to escape - sign in to find the best smoke alarms or join Which? to get access to all our lab-tested reviews.

Are block plug adaptors dangerous?

Fire safety experts prefer extension leads to block plug adaptors, provided they are used correctly, Mr Benham said.

'Block adaptors aren't unsafe but the weight of the plugs and the leads can start to pull the adaptor out of the wall socket leading to resistance heating and increasing the risk of a fire,' he said.

'Plastic block adaptors that have lots of sockets and sometimes come without a fuse are always best avoided.'

He added there were risks to buying cheap extension leads from online marketplaces.

'Be wary of cheap extension leads - they are almost always cheap for a reason. It's not worth the risk,' he said.

'The best way to protect you and your family from potentially dangerous goods is to buy from a reputable retailer.'

This advice doesn't just apply to extension leads.

Our research has found online marketplaces are often flooded with illegal or unsafe electrical goods, including so-called ‘smart’ tech. To help you shop safely, read our guide on what you need to know before you buy from these sites.

How much your appliances cost to run:  Which? reveals the running costs of household appliances, plus tips to reduce your energy bills at home

Should you charge your phone overnight?

He also warns care should be taken with USB charging.

"Adaptors with several USB charging ports can also be overloaded," he said.

"Take care not to charge laptops or mobile phones overnight and ensure you don't plug too many items into the same adaptor at any given time.

"We advise people to buy electronic goods from reputable retailers and to stop using them immediately if their chargers are showing any signs of heating or damage."

Seeking to buy a new phone? Read our mobile phone reviews.

What are surge protectors for, and when should you use them?

A surge protector is an appliance or device designed to protect electrical devices from voltage spikes.

A surge protector attempts to limit the voltage supplied to an electric device by either blocking or shorting to ground any unwanted voltages above a safe threshold.

Surges are typically produced from:

• Internal tripping, such as lights being turned on and off.
• When high-powered devices switch on, they can cause voltage fluctuations that may affect sensitive electronics.
• Direct lightning strikes can also produce huge surges from up to 2km away. Surges can be induced in cabling systems, even when there is no direct connection to the point of a lightning strike.

A surge protector's components degrade over time and become less effective after repeated surges. The longer it's been used for, the more at risk you are.

Some surge protectors have built-in lights designed to alert you when it needs to be replaced. But you can't fully rely on this - it's not a foolproof system.

As a rule of thumb, if it's absorbed a serious power surge you should always replace it immediately. Even without major events, surge protectors lose effectiveness over time. It's recommended to replace them every few years.

Looking to find the best energy supplier? Read our guide to the best energy suppliers for 2025.