Is It Safe to Leave an Oil-Filled Radiator On Overnight? (UK)

Oil-filled radiators are one of the most popular plug-in heaters in the UK. They’re quiet, they give off a gentle heat, and they keep warming the room for a while after they switch off. That makes it tempting to leave one ticking over in the bedroom all night. Here’s what the fire services and the manufacturers actually say, what it costs, and how to use one safely.

What the fire services say

• Hertfordshire Fire and Rescue Service: “Turn them off when you leave the room, leave the house or go to bed,” “unless the manufacturer specifically states that the heater is designed for safe overnight use.”
• West Sussex Fire and Rescue Service: don’t “leave the heater unattended while it is ignited or you are asleep”.
• Electrical Safety First, as quoted by the Fire Industry Association: make sure a heater “is never left unattended for long periods while in use, or while you are asleep”.

Hertfordshire’s wording is the useful one, because it tells you what to look for: a clear statement from the manufacturer. If your heater’s manual doesn’t say it’s designed for safe overnight use, follow the fire service and switch it off at bedtime.

What the manuals say

We read the instruction manuals for popular models. They don’t directly address sleeping with the heater on, but they’re firm on how and where to use it:

• Clearances. De’Longhi’s Dragon 4 manual says: “The heater must be positioned at least 50cm from furniture or other objects.” Dimplex’s OFX manual asks for at least 75mm of clear space around the radiator. The fire service figure of a metre from anything that can burn is the stricter one, so use that.
• Never cover it. De’Longhi: “never under any circumstances cover the appliances during operation, as this would lead to dangerous overheating.” Another of its Dragon 4 manuals says not to place items over the radiator, “such as to dry washing”.
• Upright only. “Always operate the heater in upright position only (wheels on the bottom, controls on top).”
• No extension leads. De’Longhi says “extension leads must not be used in powering this appliance”.
• Not in the bathroom. Both De’Longhi and Dimplex warn against bathroom use. Our guide to electrics and plug-in appliances explains why sockets and water don’t mix.
• Vulnerable people. De’Longhi says not to use the heater in small rooms occupied by people who can’t leave the room on their own, unless “constant supervision is provided”, and that children under 3 should be kept away unless continuously supervised. It also warns that “some parts of this product can become very hot and cause burns.”

The bedroom checklist

If your manual allows overnight use, or you’re using the heater in a bedroom while you’re awake, these are the rules from the fire services and manufacturers above:

1. One metre clear from the bed, bedding, curtains, clothes and anything else that can burn.
2. Nothing on it. No drying socks or towels on the fins, ever. Hertfordshire Fire and Rescue says: “Never use a portable heater for drying clothes or towels.”
3. Wall socket, not a lead. Hertfordshire also warns against overloading sockets and using “coiled cable drums”. Our guide to extension leads and tripping fuses explains why leads overheat with high-power appliances.
4. Stable and upright, on a flat floor where it can’t be knocked over. Hertfordshire suggests choosing a model with tip-over protection if possible.
5. A working smoke alarm on every level, tested regularly.
6. Children and pets kept away from the hot fins, as the manual warns.

A better way: heat the room while you’re in it

Hertfordshire Fire and Rescue says portable heaters “shouldn’t be left running when a room is unoccupied”, so don’t set a timer to heat an empty bedroom while you’re downstairs. Instead, switch the heater on when you go up, run it while you read or get ready for bed, then switch it off before you sleep. Many oil-filled radiators have a thermostat, and some, like the De’Longhi below, also have a timer, which is useful as a back-up switch-off if you forget. The oil inside stays warm and keeps giving off heat for a while after it switches off, and the radiator stays hot to the touch for a while too. If you still feel the cold overnight, a better-insulated duvet, or an electric blanket designed for all-night use, heats you directly for far less power. And if you wake up cold in the small hours, our guide to waking up at 3am because of bedroom temperature looks at why.

What it costs to run all night

At Ofgem’s price cap rate of 26.32p per kWh for October to December 2026 (Direct Debit), here’s the maximum cost per hour at each setting of a typical 2kW model with three power levels:

Those are worst-case figures, assuming the heater draws full power for the whole time. With the thermostat set, it should switch on and off to hold the room temperature: De’Longhi’s manual says that once set, “the thermostat will then adjust the set temperature automatically and keep it constant”. So the real cost depends on how cold the room is and how well it holds heat. Our cheapest way to heat one room guide compares other options.

Check it’s not on a recall list

Heaters do get recalled. West Sussex Fire and Rescue suggests registering appliances up to 12 years old on the Register My Appliance website, which says registering means you’ll “be the first to know of any safety repairs or recalls”. The government also publishes product safety alerts and recalls on GOV.UK. Hertfordshire Fire and Rescue also says to check heaters, plugs and cables regularly for damage and replace unsafe equipment. Stop using a radiator that smells of burning or leaks oil.

Frequently asked questions

Sources

• Hertfordshire Fire and Rescue Service — Portable heater safety
• West Sussex Fire and Rescue Service — Electrical safety
• Fire Industry Association, quoting Electrical Safety First — Electric heaters may pose fire risks
• De’Longhi, via Appliances Direct — Dragon 4 instruction manual
• De’Longhi — Dragon 4 instructions (TRD4)
• De’Longhi — Dragon 4 instructions (TRDS4)
• De’Longhi — Dragon 4 TRDX40820E
• Dimplex, via Heatershop — OFX oil-filled radiator instructions
• Register My Appliance — Register my appliance
• GOV.UK — Product safety alerts, reports and recalls
• Ofgem — Changes to the energy price cap, 1 October to 31 December 2026
• FireAngel — ST-622T standalone smoke alarm
• Scottish Government — Fire and smoke alarms in Scottish homes

Related reading: our cheapest way to heat one room, heat pump vs electric heater running costs and should I turn the heating off at night?