Extension sockets and adapters

There are several safety related issues concerning plugging appliances either into double adapters, modern multiple extension sockets, or long extension leads. There are multi socket extension cables with room for up to 6 different appliances so it’s very easy to overload.

As long as their combined usage doesn’t exceed 13 Amps you can safely plug in and use up to 6 electrical products. However, it is very easy to overload these devices and many people don’t realise how easy. Overheating and eventually a risk of fire can be caused by as few as just 2 appliances if they use a lot of electricity – eg. washing machine and a kettle.


Using appliances with plug adaptors or multiple socket extension cables

A radio, phone charger, two lamps and a wireless router for example would potentially only add up to less than 3 amps. But you can dangerously overload an extension with just a washing machine and a microwave.

Washing machines, tumble dryers and dishwashers all use so much electricity that they should never be used together on the same wall socket. They usually use between 10 and 13 amps.

Extension cables with just one socket at the end

An extension cable with just one socket is preferable to a multi socket one. But it’s not ideal to plug a washing machine, dryer or dishwasher permanently into any extension cable because it introduces an extra risk of electrical overheating as well as extra potential bad connections.

Miele for example say in their washing machine instruction book –

Do not connect via an extension lead. Extension leads do not guarantee the required safety of the appliance (e.g. danger of overheating)  ”


Many white goods appliances are plugged into extension cables. Anyone deciding to do so should at least use the right type of extension cable. You cannot use a 2 core extension cable which has no earth. If you do, although your machine will work, it is in a potentially lethal condition because it isn’t earthed – see I get electric shocks from the machine.

You must also ensure the cable is rated for 13 Amps. Many extensions have thinner cable than that of the washing machine.

This is an indication that the cable is meant for lawn mowers, lamps etc and not large white goods. If the cable is just as thick or thicker than that of your appliance then it should be 13 Amp and 3 core (with an earth lead).

Don’t assume anything though, check. Using a 5 or 10 Amp rated cable can cause overheating and is dangerous. Using cable that has no earth can kill if your appliance develops an insulation fault.


Wind up extension cables

Finally, note that extension cables that wind up must be fully unwound when in use. This type of extension cable will have two ratings written on it in amps. You will see that when wound up, or not fully unwound, the unit cannot take as many amps as when it is fully unwound.

For washing machines, dishwashers and tumble dryers (that can draw close to 11 amps) they need to be fully unwound or they can get hot and overheat. In fact many of these wind up extension reels are only rated for 10 Amps so avoid.


Try to avoid extensions and adaptors

There is a dilemma regarding extension leads and adaptors. Firstly, they exist, and are sold in their millions. Therefore they must be safe. Yet it’s likely that any appliance user manual will advise that they are not to be used. This is a puzzling contradiction. If they are dangerous, they couldn’t be legally sold in the UK.

However, manufacturers know that an extension lead is a third party component added to their appliance which can develop faults which they have no control over. Many extension sockets are very cheap, and don’t seem to be made of high quality materials. Some extension cables can also be very long. Extending the length of an appliances mains cable is not ideal.

Neither is adding extra electrical connections between the appliance plug and the wall socket. Here is what my Miele tumble dryer user manual says on the subject –

Do not connect the appliance by an extension lead, multi socket adaptor or similar. These can overheat and are a fire hazard  ”


So there we have it. However, as I said, if they are genuinely a fire hazard – how come they are happily sold in their millions – and in virtually every house in the country? The truth is they are an extra potential for something to overheat in high current appliances. If you can, always plug a washing machine, dishwasher, tumble dryer (or any appliance with a heating element inside) directly into a wall socket.

If this is impossible, and you have to use an adaptor or extension cable then use a good quality one. Use one as short as possible. Regularly check the plug where it plugs into the wall socket. Regularly check the individual sockets on the extension lead as well as the appliance’s plug. Look out for discolouring where it’s might be overheating and melting the plastic. Do not ignore anything like that.


Strange fishy smell near washing machine or when appliance is running?

Beware of a strange fishy smell coming from the kitchen or laundry room (unless you have some real fish in there of course).

We experienced such a puzzling smell for several days in our kitchen before I eventually tracked it down to electrical overheating in a plastic 13 amp plug.

A bad connection was causing sparking and burning and the plastic gave off this weird smell. I’m currently getting exactly the same smell when I turn a light on in a room at the back of my garage and I know it’s caused by melting plastic used in plugs, sockets, adaptors and light fittings.

If you get such a strange fishy smell near any of your appliances check the plugs and sockets for dangerous overheating.

Check if you are overloading a socket with this tool

The overload Socket Calculator is brought to you by Electrical Safety First.

How to work out how many amps your appliances use

If the Electrical Safety First tool above doesn’t help, or you want to make more accurate calculations you can work it out for yourself. It’s easy enough. You need to work out how many amps each appliance uses and make sure the combined total does not exceed 13 amps.


The amps an appliance uses can be worked out by dividing the wattage by the voltage (Amps = watts divided by voltage). In the UK the voltage is officially 230 volts (but in practice can be up to 240 volts). So a 1000 watt appliance divided by 240 (volts) is 4.16 amps. Do not go on what fuse the appliance takes, that is not how many amps it uses.

rating plate Electrical appliances have a rating plate showing how many watts it uses (see list below for help finding it). The photo above shows the rating plate of my toaster. It says it uses 780 – 930W. It’s unusual to show a range, but clearly we need to use the highest so we start with 930W (Watts). If we divide 930 by 240 (volts) we get 3.875. So the toaster uses 3.87 Amps.

My dishwasher’s rating plate (on the inside of the door) says it uses 1930W. So 1930 divided by 240 is 8.04. The dishwasher uses 8.04 Amps. The toaster and dishwasher running from the same socket would use 11.91 Amps. This is below the 13 Amp maximum.

Help finding appliance rating plates

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72 thoughts on “Extension sockets and adapters”

  1. I know you should completely unwind an extension cable before use, but it is safe to use a charger cable only partially unwound, (ie when charging a phone, tablet, etc?)
    The reason I ask, is that cable storage tidies are available that allow you to only unwind exactly the amount of cable you need to prevent trailing wires when charging small devices.
    This doesn’t sound very safe to me, but is it ok to do?

  2. Overheating of cables in coiled positions is something I associate with mains cabled because of the current they carry. Chargers usually have a large plug containing a transformer that reduces the current to low voltages. The charger plug usually gets quite hot but is designed to do so. For that reason they need air circulating around them. The thin cable that plugs into the device is probably only carrying a fraction of the voltage so it may not be subject to the same overheating concerns but I can’t reliably say whether it’s ok or not. I would expect if it was an issue though that the instructions for the cable storage device or printed somewhere on it there ought to be a warning as there is on mains cable extensions that come in a wound reel.

  3. Many thanks, Andy, thats very helpful.
    The ability to leave the cable coiled is actually used as a main selling feature for these cable tidy devices, so I’m sure you are right in that if it were a concern, there would be a requirement to place a warning on them.
    Much appreciated!

  4. I have just purchased a Beko under counter frost free freezer, but the plug is to short to reach my socket, and the instructions say dont use an extension cable, why is this?? and would it be OK to use an extension cable?

  5. I have my fridges and freezers all connected via an extension cable. If the extension cable is good quality, and not very long and not overload I can’t see what the problem would be. Extension cables do introduce the possibility of overloading, if really long potential drops in current and potential extra connection faults so maybe they just want to discourage it but extension cables are a legitimate product used by millions of people and designed specifically to extend the reach of wall sockets.

  6. Hello Pauline. As long as the extension is 13 Amp, (thick cable and with a 13 amp fuse in plug) and wall socket is 13 amp (check it has a 13 Amp fuse) and as long as you don’t plug appliances needing more than 13 amps combined I can’t think of an issue. If any don’t have a 13 amp fuse you can’t rectify it by fitting a 13 amp fuse – the cable will not be designed for 13 amp!

  7. Hello, the only wall socket available for my combi grill/ oven/microwave is about 2 cms too far. All the advice online seems to be to never use an extension with a microwave. Please cheer me up and tell me this aint necessarily so.

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