Extension Leads and Overloaded Sockets: Staying Safe
How to use extension leads and adaptors safely in a UK home, how to tell if a socket is overloaded, which appliances to avoid and when more sockets are the answer.
Extension leads are handy, and most homes have several. They are also a common cause of overheating and electrical fires when misused. The good news is that safe use comes down to a few simple habits. This guide explains how to spot overload, how to choose and use leads, and when it is time to get proper sockets installed.
How overloading happens
Every socket on a standard UK circuit can supply a limited current, and a typical plug-in extension lead is rated for around 13 amps in total, equivalent to roughly 3,000 watts. If the combined load of everything plugged in exceeds the rating, the cable and connections heat up. The fuse in the plug or the protective device at the consumer unit may trip, but heat damage can start before that happens.
Heavy appliances use the most. Heaters, kettles, toasters, irons and washing machines can each draw a large share of the rating on their own.
Appliances to keep off extension leads
Plug these straight into a wall socket where possible:
- Space heaters and fan heaters.
- Kettles, toasters and air fryers.
- Washing machines, tumble dryers and dishwashers.
- Microwaves and large cooking appliances.
- Portable air conditioners and dehumidifiers.
Low-power items, such as lamps, phone chargers and TVs, are generally fine on a lead if the total is well within the rating.
Choosing a lead
- Check the rating. The label gives the maximum current and wattage.
- Buy from a reputable source. Poorly made leads can be unsafe.
- Pick the right length. Long leads are more likely to be tangled and trip people up.
- Consider a surge-protected lead for sensitive electronics, but do not rely on it to prevent overload.
- Use a fully unwound reel for cable reels carrying heavy loads, because coiled cable can overheat.
Safe habits
- Do not daisy-chain extension leads or plug adaptors into each other.
- Keep leads away from heat sources, carpets and furniture legs.
- Do not run leads under rugs or through doorways where they can be damaged.
- Unplug items you are not using, particularly in bedrooms.
- Check plugs and cables regularly for scorching, cracks or exposed wire.
- Never use a lead that is warm to the touch.
Signs of trouble
Stop using the socket or lead and unplug everything if you notice:
- A burning smell or discolouration around the plug or socket.
- Warm or hot plugs and sockets.
- Buzzing, crackling or sparking.
- Fuses that blow repeatedly.
- Loose plugs that fall out of the socket.
If the socket itself is damaged, treat it as a fault for an electrician rather than as a lead problem. See signs of dangerous wiring for more warning signs.
When it is time for more sockets
If you rely on several extension leads in one room, the real fix is more wall sockets in the right places. A registered electrician can assess the circuit and advise. Read adding extra sockets and USB sockets for what is involved and typical costs.
Outdoors and in rented homes
Outdoor use needs equipment rated for the weather and an RCD. In a rented property, tell your landlord if you do not have enough sockets, rather than relying on temporary arrangements.
A worked example
A home office has a laptop, two monitors, a lamp, a desk fan and a small fan heater, all on one four-way lead plugged into a single socket. The monitors and laptop are modest loads, but the fan heater alone is around 2 kW. Add the rest and the lead is working near the limit of its 13 amp rating for hours at a time. The sensible fix is to give the heater its own wall socket or choose a different way to heat the room, and to plan for more sockets if the lead keeps being needed. A quick estimate with the wattage labels is all it takes to see the risk.
A quick load check
- Find the wattage on the label of each device, or amps if only that is shown.
- Add them together.
- Compare the total to the lead's rating, which is on the label.
- Keep the total well below the rating, and remember that heaters are the big users.
As a rough guide, 13 amps at 230 volts is around 3,000 watts, so two fan heaters at 2 kW could not share a lead safely.
Common mistakes
- Using a cable reel coiled up while it carries a heavy load.
- Plugging a lead into an adaptor on the back of a socket.
- Leaving a lead under a rug or behind a radiator.
- Using a lead that has been repaired with tape.
- Assuming a surge-protected strip also protects against overload.
Edge cases
- Rented homes: ask the landlord for more sockets rather than permanently relying on leads.
- Older homes with few sockets: consider a socket plan with an electrician rather than a patchwork of leads.
- Garden and garage use: outdoor-rated equipment and RCD protection are essential, and long reels should be fully unwound.
- Children and pets: keep leads out of reach and consider cable covers.
When to call a professional
If a socket itself is warm, discoloured or loose, stop using it and switch off at the consumer unit. A registered electrician should check the socket and the circuit behind it.
Frequently asked questions
Can I plug an extension lead into another extension lead?
Avoid it. Chaining leads makes it hard to know the total load and increases the risk of overheating at the connections.
Are adaptors worse than extension leads?
Multi-way adaptors that plug straight into the socket put stress on the socket and can be easily overloaded. A lead with a built-in rating is usually a better choice.
Should I leave extension leads plugged in overnight?
Low-power items on a sound lead are generally fine, but unplugging heating equipment and anything that gets warm is wise.
How many amps can a standard extension lead take?
Most are rated for 13 amps in total, but always check the label, since some are rated lower, particularly cable reels that are coiled.