How much does an oil-filled radiator cost to run?
A 2kW oil-filled radiator costs about 53p an hour while its element is on, at the Ofgem cap rate of 26.32p/kWh. Once the room is warm the thermostat switches the element off and on. If it is only on half the time, a six-hour evening costs about £1.58 rather than £3.16.
Prices last checked: 26 September 2026 · Source: Ofgem energy price cap, 1 October to 31 December 2026 · Great Britain average, standard variable tariff, paid by Direct Debit
What an evening really costs: it depends on cycling
Oil-filled radiators are the heater people most often assume is "cheap to run". The oil does not make electricity go further. What it does is store heat, so the element can switch off for longer stretches while the fins keep radiating. The table shows a 2kW radiator on for a six-hour evening at different duty cycles (the share of time the element is actually on).
| Room situation | Element on | Energy used | Cost per evening | Per 30 evenings |
|---|---|---|---|---|
| Cold room, thermostat on max | 100% | 12 kWh | £3.16 | £94.75 |
| Draughty room, high setting | 75% | 9 kWh | £2.37 | £71.06 |
| Average room, mid thermostat | 50% | 6 kWh | £1.58 | £47.38 |
| Small insulated room, door shut | 30% | 3.6 kWh | 95p | £28.43 |
How to run an oil-filled radiator for less
- Turn the thermostat down, not the power switch. On high power with a moderate thermostat, the room warms quickly and then the element cycles. Leaving the power on "low" but the thermostat on maximum means the element never cuts out.
- Switch it on before you need it, then let the stored heat work. Oil radiators are slow to warm up. Using the built-in timer to start 30–45 minutes early is cheaper than running it on full while you sit there waiting.
- Switch off before you leave the room. The oil keeps radiating for a while afterwards. You get that heat free whether you stay or not.
- Don't cover it or push it against furniture. Blocked fins trap heat around the thermostat, so it cuts out early and the rest of the room stays cold. That's also a fire risk, and most manuals forbid it.
- Keep it off the outside wall if you can. A radiator under a single-glazed window sends a lot of its heat straight outside.
Oil-filled radiator vs other ways to heat a room
vs fan or convector heater
Same cost per hour at the same wattage. The radiator gives steadier, quieter heat and keeps warming the room after it cycles off. A fan heater is better for a 10-minute blast in a bathroom.
vs gas central heating
Gas is cheaper per kWh of heat (7.97p/kWh at the cap, before boiler losses, against 26.32p). A radiator only saves money when it lets you turn the whole-house heating down or off. See the 2kW heater page for the break-even maths.
vs storage heaters
Storage heaters charge on cheap overnight electricity, if you have an Economy 7 or similar tariff. A plug-in radiator used in the evening pays the day rate. If you already have storage heaters, use them first.
vs heating yourself
An electric blanket or heated throw uses a small fraction of the power. For one person sitting still, it is the cheapest option by a wide margin.
Mistakes that make the estimate wrong
- Believing "cheap to run" claims. A 2kW oil radiator and a 2kW fan heater draw the same 2kW whenever their elements are on.
- Multiplying the rating by the hours. That gives the maximum, not the likely figure. The duty cycle can easily halve it.
- Forgetting it runs at night. Left on in a bedroom with the thermostat high, it will cycle all night. Eight hours at full power is about £4.21.
Limits of this estimate
The unit rate is the Ofgem cap average for Great Britain, Direct Debit, standard variable tariff. Fixed tariffs, other payment methods, regional differences and Economy 7 all change your rate. The duty cycle is the biggest unknown and only a measurement will tell you what yours is.
Frequently asked questions
Do oil-filled radiators use less electricity than other heaters?
Not per hour at the same wattage. They can use less over an evening because the stored heat lets the thermostat keep the element off for longer.
How much does an oil-filled radiator cost per day?
For a 2kW model on six hours a day, somewhere between about 95p and £3.16 depending on how much the element cycles. The calculator above lets you set your own figure.
Is a 1.5kW radiator cheaper than a 2kW one?
Per hour on full power, yes (39p against 53p). In a cold room the smaller one may never reach the thermostat set point and run flat out all evening, so the saving can be smaller than it looks.
How long does an oil-filled radiator stay warm after switching off?
It depends on the size of the unit. Larger radiators with more fins hold more heat. Expect a gradual fall over tens of minutes rather than the instant drop you get with a fan heater.