The Plug-In Heater Is Fine — It’s the Extension Lead That Worries Me
Photo: John Goldsmith , CC BY-SA 2.0, via Wikimedia Commons
By the time the first proper cold snap lands in November 2026, half the country has already dug out the plug-in heater. No judgement here. A fan heater in a chilly box room or a halogen job in a garden office can be a sensible stopgap. The trouble usually is not the heater itself. It is what we plug it into: the nearest extension lead, a four-way adaptor, or a daisy chain of both. That is when a bit of winter comfort starts asking a lot of a cable that was never designed to run flat out for hours.
The maths is dull, but it is the whole story
A standard UK socket is rated at 13 amps. At 230 volts, that is roughly 3,000 watts — and that is the ceiling, not a target. A 2kW heater pulls about 8.7 amps. A 3kW heater pulls around 13 amps. On paper a 13A extension lead can cope. In practice, heaters are continuous loads: they sit there drawing close to the limit for an hour or more, while the lead is coiled behind the sofa or tucked under a rug. Add a phone charger, a lamp and a TV and you are asking for trouble. The plug may feel warm; the lead may feel warmer. That is not normal.
Coiled leads and multi-way blocks are not extra sockets
An extension lead does not create electricity. It shares what is already there. A multi-socket adaptor does the same. Plug a heater into a block that already has a kettle, a microwave or a tumble dryer on it and you can overload the circuit before the fuse in the plug has time to react. Coiled leads make it worse because heat cannot escape from the bundle. Some leads have a lower rating when coiled; even those that do not will run hotter in a tight coil. Uncoil fully, keep the lead visible, and never run it under a carpet, behind a radiator or through a doorway where it can be pinched.
Places a portable heater should never go
Bathrooms are top of the list. Portable heaters and water do not mix, and a lead trailing across a wet floor is an accident waiting to happen. Only use a fixed, suitably rated heater in a bathroom, fitted by someone who knows what they are doing. Keep heaters at least a metre from curtains, bedding, paper and furniture. Never use one to dry clothes. Do not put a heater on a shelf where it can be knocked off, and do not cover it. If you have a heated throw or electric blanket, follow the maker's instructions, check the lead and plug regularly, and plug it directly into a wall socket where possible.
What landlords should be checking before winter
Landlords cannot control every tenant's extension lead, but they can make the electrical basics sound. Check the EICR is in date and any coded issues have been addressed. Press the RCD test button and make sure it trips. Look for cracked sockets, scorch marks, loose switches and missing screws. If fixed heating is provided, make sure it works and is safe. Provide clear, plain-English guidance on heater use and avoid leaving cheap, unbranded heaters in properties. A quick PAT test on landlord-supplied appliances is cheap compared with a fire. And if the consumer unit is an old fuse box with no RCD protection, that is a conversation worth having now, not in January.
A quick room-by-room check
Living room: heater on a hard, clear surface, plugged straight into a wall socket, lead fully unwound, nothing stacked on top.
Bedroom: heated throw or blanket plugged direct, cable not trapped under the bed, no trailing lead across the floor.
Kitchen: do not run a portable heater off the same ring as the kettle, toaster and microwave; avoid multi-way adaptors.
Bathroom: no portable heater unless it is specifically designed and fixed for the zone; keep all leads away from water.
Hall and landing: watch trip hazards; do not wedge a lead under a door.
Garden office: use a properly sized supply, not a long extension lead from the house; check for RCD protection.
When to stop and call an electrician
Call us if a plug or socket is hot to touch, if there is a burning smell, scorch marks or discoloured plastic, if the fuse trips when the heater goes on, if the RCD keeps tripping, or if you hear buzzing from a socket. Warm is not the same as hot. If in doubt, unplug it and get it checked. A dedicated heater socket, a circuit check or an RCD upgrade is usually less dramatic than the alternative.
