Homeowner guide
Extension leads — done safely
Extension leads are one of the top causes of accidental electrical fires in UK homes. The rules are simple — know the 3kW total limit, never chain leads together, and unroll the cable before you load it up.
Quick check the load in your head
Add up the wattage printed on the label of every appliance on the lead. If the total is over 3,000W — or if you're not sure — take something off. Try our socket load calculator to work it out.
Three rules that prevent most fires
One 13A socket = 3,000W total
A single BS 1363 socket is protected by a 13A fuse in the plug and a 32A ring/20A radial upstream. The plug fuse is the hard limit — 13A × 230V ≈ 3,000W. That is the total for everything on that lead, not per outlet. Two monitors, laptop, phone chargers, printer: fine. Add a 2kW fan heater: overload.
Never plug one extension into another
Daisy-chaining bypasses the 13A fuse protection for the downstream lead and multiplies the connections that can loosen and overheat. A single 4- or 6-way lead from a wall socket is safe; a 4-way into a 4-way is not. If you need more sockets, fit more sockets.
Fully unroll cable reels before loading them
A partially wound extension reel carrying anything close to its full current turns the drum into a heating element — the tightly coiled cable cannot dissipate heat and the insulation melts. Unroll the full length before plugging anything heavy in. Most reels have a much lower rating when coiled (often marked 3.1A vs 13A fully out).
Buying a good extension lead
- • Branded manufacturer with a UKCA or CE mark.
- • Individually switched sockets — you can kill just the one appliance.
- • Fused 13A plug on the incoming lead (all UK leads should have this — check).
- • Built-in surge protection is a bonus but not a substitute for a Type 2 SPD at the consumer unit.
- • For outdoor use, IP54 or better with a proper flap over each outlet.
Never do this
- ✕Plug a fan heater, oil-filled radiator, tumble dryer or kettle into an extension lead.
- ✕Run an extension lead under a rug, carpet or across a doorway.
- ✕Use an indoor lead outside — buy an IP54+ outdoor lead with an RCD adaptor.
- ✕Use unbranded, unfused travel adaptors bought from marketplace sellers.
- ✕Ignore a warm plug, discoloured socket face, or a smell of hot plastic.
Running out of sockets?
Extra double sockets, USB-C outlets, dedicated 20A radials for a home office, garage or workshop — a small job that removes the trailing leads for good.