Are electric heaters safe to leave on, and what do they cost to run this winter?

The short answer: not while you are out or asleep

Used with care, a plug-in electric heater is a reasonable way to warm one room. Fire safety advice draws the line at leaving it on with nobody there. The National Fire Chiefs Council (NFCC) says to unplug heaters when you go out or go to bed, and Electrical Safety First says never to leave a heater unattended while it is in use or while you are asleep. London Fire Brigade says heater fires typically start when bedding, blankets or clothes are placed too close.

Electrical Safety First does not recommend running a portable heater overnight. For a warm bedroom, it suggests warming the room before bedtime: an oil-filled radiator keeps a room warm for quite a while after it is switched off.

The rules for any plug-in heater

Plug it straight into a wall socket. The NFCC says electric heaters are high powered and belong in a wall socket, not an extension lead, which is easily overloaded. Electrical Safety First says extension leads are rated at 13 amps, some older ones at 10, and that an overloaded lead, or the plug in the wall, can overheat and cause a fire.

Keep a clear metre around it. Electrical Safety First’s distance is at least one metre from anything that can burn, such as paper, furniture and curtains, and London Fire Brigade says to sit at least a metre away, as a heater could set light to your clothes or chair. The NFCC asks for extra care if anyone at home uses emollient skin products, which can make clothing and soft furnishings more flammable.

Never dry clothes on or close to it. Stand it on a level surface where it won’t be knocked over or block your way out. The NFCC says standard portable heaters must not be used in bathrooms or shower rooms, and must only be moved once switched off and cooled down. Keep a working smoke alarm on every floor.

Check for a recall before the first cold night

Heaters often come out of storage after a long time unused, the NFCC notes, so check yours hasn’t been recalled. The Office for Product Safety and Standards publishes recalls and safety notices on GOV.UK in its Product Safety Alerts, Reports and Recalls list, which you can search by product. Manufacturers can also announce recalls themselves, so check the maker’s website too, using the model number on the label. For an electric heater that is getting older, London Fire Brigade’s advice is to have it tested by a qualified electrician or buy a new one.

Register the heater with its manufacturer so you can be contacted about a recall. When buying, Electrical Safety First advises using a reputable retailer rather than a third-party online seller, and avoiding second-hand heaters, which may not meet current safety standards.

Fan, convector, oil-filled or halogen: what differs

Electrical Safety First describes four common types. A fan heater blows air over a heated coil: usually small, it gives instant heat but can be noisy. Its vents need keeping clear of dust and fluff, and its hot air can be intense, so keep it away from curtains, bedding, furniture and people. A convector heater warms the air, which rises and circulates until the room reaches the set temperature; it is usually larger, warms the room more slowly and needs clear space above and around it, and it can overheat if its grilles are blocked or dust builds up inside.

An oil-filled radiator heats a reservoir of oil that warms metal fins. It is slower to warm up but keeps giving out heat after it is switched off, and Electrical Safety First calls it generally more economical to run; keep children away from the fins until they cool. A halogen heater radiates infrared light that heats objects directly rather than the air: keep it well away from curtains, bedding, furniture and people, and choose one with a tip-over switch.

Whatever the type, wattage sets the most a heater can cost in an hour: at full power, a 2 kW fan heater and a 2 kW oil-filled radiator use the same electricity.

What it costs to run this winter

The sum is the heater’s power in kilowatts (kW) times the price of a kilowatt hour (kWh) of electricity. The power is on the heater’s label or in its instructions: 2,000W is 2 kW. Ofgem’s price cap for 1 October to 31 December 2026, announced on 26 August, gives an average of 26.32p per kWh on a standard variable tariff paid by Direct Debit, across England, Scotland and Wales. That figure includes no VAT: the government has cut VAT on household electricity in England, Scotland and Wales to zero from 1 October 2026 to 31 March 2027, HMRC confirms. In Northern Ireland, electricity stays at 5% VAT.

At full power, for a four-hour evening (say 6pm to 10pm):

1 kW: 26.32p an hour, or £1.05 an evening.

2 kW: 52.64p an hour, or £2.11 an evening.

3 kW: 78.96p an hour, or £3.16 an evening.

Rates vary by region and payment method, so on a fixed deal, another payment method or in Northern Ireland, use the unit rate on your bill; on Economy 7, use the rate for the hours the heater runs. The standing charge is paid either way, so it doesn’t change these sums. The next cap period starts on 1 January 2027, and Ofgem will announce its level by 25 November (what we know about January).

Why real use is often lower

Those figures assume the heater runs flat out all evening, so treat them as a ceiling. If your heater has a thermostat, it works much the way the Energy Saving Trust describes a room thermostat: it heats until the room reaches the temperature you chose, then switches off until the room cools slightly. Once the room is warm, the heater is off for part of each hour, so real use is often lower, by an amount that depends on the room, the weather and the setting.

Set it to a comfortable temperature rather than the maximum. The Energy Saving Trust suggests the lowest comfortable temperature, for most people between 18°C and 21°C, and UKHSA advises trying to heat the rooms you spend a lot of time in to at least 18°C.

Electric heater or gas central heating?

Unit for unit, gas is cheaper. The same cap sets gas at an average of 7.97p per kWh, including 5% VAT, so a unit of electricity costs about 3.3 times as much.

A plug-in heater loses no heat up a flue and a boiler loses some, but that doesn’t close the gap: even if a boiler turned only 80% of its gas into heat, a unit of heat from it would cost about 10p, against 26.32p from a plug-in heater. As the Energy Saving Trust puts it, even though electric heating is more efficient than a boiler, “the higher cost of electricity more than offsets this”, and those costs are especially noticeable when electric heating warms an entire home. That is why heating a whole house with plug-in heaters usually costs more.

One room for a few hours is a different sum, because you pay for how many units you use as well as their price, and a plug-in heater warms only the room you are in while central heating warms every room with a radiator on. The heater comes out cheaper only when the boiler would burn more than 3.3 times as many kWh of gas as the heater uses in electricity, which is likelier for one person in one room than for a whole household. The Energy Saving Trust says a portable heater can be useful when you want to warm up just one room for a little while, but adds that although these heaters warm a single room rather than the whole home, they “can be expensive to run”, because the electricity they use costs more per unit of heat than main heating such as gas. A smart meter’s in-home display lets you compare an evening each way.

Carbon monoxide: a gas and paraffin heater risk

UKHSA describes carbon monoxide as a by-product of fuel burning without enough oxygen. An electric heater burns no fuel, so it produces none; the NFCC’s carbon monoxide alarm advice is for rooms with fuel-burning heating that doesn’t run off electricity.

Portable gas and paraffin heaters burn fuel in the room. The NFCC says to use them only in well-ventilated areas, having checked they are suitable for indoor use, with a carbon monoxide alarm in the same room, and never to use a portable gas heater in a bedroom; outdoor heaters must never be used indoors. Know the symptoms of carbon monoxide poisoning: if an alarm sounds or you suspect a leak, UKHSA’s advice is to stop using all appliances, leave the property, call the National Gas Emergency Service on 0800 111 999, stay out until the emergency services say it is safe, and get medical help. In Northern Ireland, the gas emergency number is 0800 002 001.

If the bill is the worry

Check what you are owed before you ration heat. The Warm Home Discount is a one-off £150 off your electricity bill; the scheme reopens in October 2026 and is usually applied automatically if you are eligible, though in Scotland you may need to apply to your supplier. It isn’t available in Northern Ireland. A Cold Weather Payment of £25 is paid automatically to people on certain benefits for each seven-day spell of very cold weather between 1 November 2026 and 31 March 2027; it isn’t available in Scotland, where you might get a Winter Heating Payment instead.

If you are struggling to pay, tell your supplier: Ofgem says suppliers must help if you ask, for example with a repayment plan or emergency credit. If you have reached State Pension age, are pregnant or have young children, or live with a disability or long-term medical condition, among other reasons Ofgem lists, ask your supplier to add you to its Priority Services Register, which UKHSA calls a free support service. And the cheapest warmth costs nothing to run: how to stay warm without the heating on.