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How to use an extension lead safely

Updated: 23 October 2026

The empty sockets behind the sofa look like spare capacity. How to use an extension lead safely is mostly about what you do not add: a second lead, a kettle beside a toaster, or a higher fuse than the one that blew. One lead, one wall socket, and the marked amps. This page is from the Products Compared editorial team, using Electrical Safety First, London Fire Brigade and the limits on the twelve listings in our [extension lead comparison](/hub/sockets-and-extension-leads/extension-lead). We did not run a lab test. A qualifying Amazon purchase can earn us a commission at no extra cost to you.

The empty sockets behind the sofa look like spare capacity. How to use an extension lead safely is mostly about what you do not add: a second lead, a kettle beside a toaster, or a higher fuse than the one that blew.

Our top picks

Masterplug Masterplug 4-way switched 2 m

Best overall

Masterplug Masterplug 4-way switched 2 m
9.6/10about £9.50
View offer
Masterplug Masterplug 4-way 5 m

Alternative

Masterplug Masterplug 4-way 5 m
9.4/10about £9.99
View offer
Desiretech Desiretech 4-gang 2 m

Best value

Desiretech Desiretech 4-gang 2 m
9.2/10about £6.99
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On this page
  1. 1.Plug one lead into one wall socket
  2. 2.Add up the heavy appliances before you fill the sockets
  3. 3.Lay the cable so it is not taut, trodden on or taped
  4. 4.If the fuse blows, do not fit a bigger one
  5. 5.When to stop and get a registered electrician

Plug one lead into one wall socket

Put the plug straight into the wall socket, and stop there. Electrical Safety First says not to daisy-chain: one extension plugged into another overloads the first plug, even when the second bar still has empty sockets. Empty sockets are not a second 13 A supply. If the cable does not reach, use one longer lead or a new socket, not a second strip. A 2 m Masterplug will not become a 5 m lead because you add another bar on the end. What to buy is on the extension lead buying guide.

Add up the heavy appliances before you fill the sockets

Most domestic leads are 13 A. Some older leads are 10 A, so read the marking on the one you have. Thirteen amps at 230 V is 2,990 W. A seller’s 3,250 W line does not raise the fuse. Filling six sockets does not multiply that total, and switches do not add capacity, because one fuse still protects the strip. London Fire Brigade says a kettle, a toaster, a microwave, a tumble dryer and a heater should not share an extension. A lamp, a router and a phone charger are the usual group, if you still add the rating plates. The DEWENWILS bullet describes a 13 A resettable breaker. If it trips, unplug something before you reset it.
Masterplug Masterplug 4-way switched 2 m

Testsieger

Masterplug Masterplug 4-way switched 2 m
9.6/10about £9.50
View offer

Lay the cable so it is not taut, trodden on or taped

Run the cable where you can see it, with a little slack. County Durham and Darlington say not to stretch it taut, and to cover a run that crosses a path. Do not hide the spare under a rug or a sofa. Coiled flex under a load can heat, and tape is not a repair. If the sheath is split, that lead is finished. Match the length, then lay this one cable loosely. How to choose the metres is on how long an extension lead. A cable reel is a different product: unwind it fully before you load it.

If the fuse blows, do not fit a bigger one

The fuse in a BS 1363 plug is there to fail before the flex does. Electrical Safety First says to replace a fuse like for like. A 3 A fuse and a 13 A fuse are the usual sizes, and the appliance plate wins over a guess. Fitting a 13 A fuse where a 3 A fuse blew hides the overload. Stop if you smell hot plastic, see scorch marks, or the fuse blows again with nothing extra plugged in. A dark surge light, when the seller says the light means protection is present, means you stop treating the bar as surge protected. Unplug at the wall, and do not open the strip.

When to stop and get a registered electrician

Stop buying leads when the strip has become the room’s permanent wiring. Electrical Safety First’s point is that a house which only works with strips needs more sockets, fitted by a registered electrician. Burnt pins, a cracked plug, a warm socket and a fuse that will not stay in are the same handoff. Bathrooms, outdoors and any flex that must be reterminated belong with a qualified person. HSE guidance HSG107 is a workplace regime, not a living-room PAT schedule. At home: one ready-made lead, inside its amps, unplugged if it smells or scorches.

Common questions

Can I plug one extension lead into another?
No. Electrical Safety First and Dorset and Wiltshire Fire and Rescue Service both say not to daisy-chain. The first plug and the wall socket carry everything on the second lead. If you need more reach, use one lead that is long enough, or have a socket fitted. Empty sockets on the second bar do not create extra amps.
How many amps can I put on a normal lead?
Usually 13 A in total, not 13 A per socket. Some older leads are marked 10 A, so read the one you have. Thirteen amps at 230 V is 2,990 W. A seller’s 3,250 W line does not raise the fuse. Add the rating plates of what is switched on together, and leave the kettle, toaster, microwave and heater on the wall.
Which appliances should stay on the wall socket?
London Fire Brigade’s examples are the kettle, toaster, microwave, tumble dryer and heater. They draw too much to share a lead with each other. Lamps, chargers, routers and a television are the usual contents of a strip, provided the total stays inside the marked amps and the lead is not coiled or covered.
What fuse belongs in the plug?
The fuse the manufacturer specifies, replaced like for like. Electrical Safety First treats 3 A and 13 A as the common guide, and the appliance plate overrides a guess. Do not fit a 13 A fuse because the 3 A fuse blew. The extension lead’s own plug is normally 13 A. That fuse protects the lead. It does not uprate the appliance.
When do I need an electrician instead of another lead?
When the lead would stay down for months because the room lacks sockets, when the plug is burnt, cracked or hot, or when you are about to use a lead outdoors or in a bathroom. Another extension does not fix those. A registered electrician fitting sockets does. Do not tape a damaged flex and keep going.

Related pages

Surge protected or basic extension lead

Extension lead

Best extension lead UK: who it fits and who should skip

Extension lead buying guide before you pick a brand

How long an extension lead should be for your room

Sources

Sources taken from the research digest. Prices and review counts are a stored amazon.co.uk snapshot, not a live check. This page did not run a lab test.

  1. SI 1994/1768 — Plugs and Sockets etc. (Safety) Regulations 1994 (retrieved 22.10.2026)
  2. GOV.UK — Electrical Equipment (Safety) Regulations 2016 (retrieved 22.10.2026)
  3. Electrical Safety First — Extension leads, cable reels and block adaptors (retrieved 22.10.2026)
  4. Electrical Safety First — Plugs and fuses (retrieved 22.10.2026)
  5. London Fire Brigade — Cables, fuses and leads (retrieved 22.10.2026)
  6. Scottish Fire and Rescue Service — Electrical safety (retrieved 22.10.2026)
  7. County Durham and Darlington Fire and Rescue Service — Extensions and leads (retrieved 22.10.2026)
  8. HSE — HSG107 Maintaining portable electrical equipment (retrieved 22.10.2026)