What should you not plug into an extension lead?

An extension lead makes it possible to supply several devices from a single mains socket, but it is not suitable for every application. The most important rule is that the combined electrical load of all connected devices must remain within the maximum load specified for the extension lead.

There is no universal list of appliances that can never be connected to any extension lead. The electrical requirements of the appliance, the specification of the extension lead and the manufacturer's instructions all need to be considered. High-powered appliances in particular require additional care because they can place a considerable load on the extension lead.

Which appliances should usually be connected directly to a wall socket?

Appliances with a high continuous power demand are generally best connected directly to a suitable wall socket, especially where the appliance manufacturer recommends this. This frequently applies to electrical heating appliances and other devices that draw a large amount of power for extended periods.

If the operating instructions state that an appliance must be connected directly to a mains socket, an extension lead should not be used. The appliance manufacturer's instructions always take priority.

Can I plug an electric heater into an extension lead?

Portable electric heaters can have a high power consumption and may operate at that level for long periods. This places a substantial continuous load on the cable, plug and contacts of an extension lead.

For this reason, a heater should normally be connected directly to a suitable wall socket unless the appliance manufacturer explicitly permits another arrangement. Never use an extension lead whose electrical rating is lower than the power required by the heater.

Can I connect a kettle, toaster or other kitchen appliance?

Kettles, toasters and many other appliances that produce heat can draw a relatively high amount of power. A single appliance may already account for a large proportion of the maximum load of an extension lead, especially if other devices are connected at the same time.

Check both the appliance rating and the permitted load of the extension lead before use. Where the manufacturer's instructions recommend a direct wall connection, follow that guidance rather than using a multi-socket extension lead.

Can I plug a microwave into an extension lead?

A microwave can require a significant amount of electrical power and may have specific requirements for its mains connection. Whether an extension lead is permitted therefore depends on the appliance manufacturer's instructions and the electrical specification of the extension lead.

If the instructions specify connection directly to a wall socket, the microwave should not be operated through an extension lead.

Can I plug a fridge or freezer into an extension lead?

Refrigerators and freezers are often intended to remain connected continuously. Their compressors can also create a higher electrical demand when starting than during normal operation. Whether an extension lead can be used therefore depends on the appliance manufacturer's requirements and the suitability of the extension lead.

For a permanent installation, a direct wall connection is generally preferable where possible. If an extension lead is considered, check the appliance instructions and ensure that the product is suitable for continuous operation and the required electrical load.

Can I plug a washing machine or tumble dryer into an extension lead?

Large household appliances such as washing machines and tumble dryers can have high power requirements, particularly when heating water or air. They are therefore commonly intended to be connected directly to a suitable wall socket.

Always follow the manufacturer's installation instructions. If a direct mains connection is specified, do not use an extension lead or multi-socket power strip as an alternative.

What happens if an extension lead is overloaded?

If connected devices draw more power than the extension lead is designed to handle, plugs, cables and electrical contacts can become excessively warm. Continued overloading can damage the extension lead and increase the risk of an electrical fault.

Warning signs can include unusual heat, discolouration, a smell of overheated plastic, damaged insulation or plugs that no longer fit securely. If any of these signs appear, disconnect the extension lead and stop using it.

How do I know whether my devices exceed the maximum load?

Check the power rating of every device connected to the extension lead and add the values together. The total must remain below the maximum electrical load specified for the extension lead. Using more socket outlets does not increase the amount of power available.

For example, connecting a second or third high-powered appliance can overload an extension lead even if several sockets are still physically unused. Our guide to the maximum load of an extension lead explains how to calculate the combined load in more detail.

Can I plug one extension lead into another?

No additional electrical capacity is created by connecting several extension leads together. Daisy chaining also introduces additional plugs and contacts into the power path, which can increase the risk of overheating or poor connections.

If the existing extension lead is too short or does not provide enough sockets, use one suitable extension lead with the required cable length and number of outlets instead. More information is available in Can you plug an extension lead into another extension lead?.

Can I use all the sockets on an extension lead?

Yes, provided the extension lead is designed for the connected equipment and the combined electrical load remains within its specified maximum. The number of occupied sockets alone does not determine whether an extension lead is overloaded.

Several low-powered devices such as chargers, monitors or small electronics can consume considerably less power than one high-powered heating appliance. Always consider the total load rather than simply counting the plugs.

What else should not be connected to an extension lead?

Do not connect equipment if its plug, cable or housing is damaged, and do not use an extension lead in an environment for which it is not designed. A standard indoor extension lead, for example, should not simply be used outdoors where it may be exposed to moisture.

You should also avoid using adapters or other accessories that create an unstable connection or prevent plugs from fitting correctly. Every component in the connection should be suitable for the intended electrical load and environment.

How can I use an extension lead safely?

• Check the maximum electrical load of the extension lead before connecting high-powered equipment.
• Add together the power consumption of all connected devices.
• Follow the appliance manufacturer's instructions regarding the mains connection.
• Do not connect one extension lead to another.
• Keep plugs, cables and socket outlets free from visible damage.
• Stop using the extension lead if it becomes unusually hot or shows signs of damage.
• Use an extension lead that is suitable for the environment in which it will be operated.
• Choose enough cable length and socket outlets so that additional adapters or chained extension leads are unnecessary.

When should I use a wall socket instead?

A direct wall connection is the better choice when the appliance manufacturer specifies it, when a device has a particularly high or continuous power demand, or when there is any doubt about whether the extension lead can safely supply the required load.

An extension lead should make power distribution more convenient without compromising the electrical requirements of the connected equipment. Choosing the correct product and respecting its maximum load are more important than simply having enough available sockets.