How much does an oil-filled radiator cost to run?
A 2kW oil-filled radiator costs 52.6p an hour on full power, a 1kW model 26.3p and a small 500W one 13.2p. Because the thermostat switches the element on and off once the room is warm, an evening usually costs less than the full-power figure.
| Per day | £1.47 |
|---|---|
| Per week | £10.32 |
| Per month | £44.71 |
| October to March | £268.25 |
| Per year | £536.51 |
Models we have worked out
- De'Longhi Dragon 4 from 52.6p an hour at full power
Cost by power rating
| Power | 1 hour | 4 hours | 8 hours |
|---|---|---|---|
| 500W | 13.2p | 52.6p | £1.05 |
| 800W | 21.1p | 84.2p | £1.68 |
| 1,000W | 26.3p | £1.05 | £2.11 |
| 1,500W | 39.5p | £1.58 | £3.16 |
| 2,000W | 52.6p | £2.11 | £4.21 |
| 2,500W | 65.8p | £2.63 | £5.26 |
Find the power rating on the label underneath or on the back of the appliance, or in its manual. It is usually written in watts (W) or kilowatts (kW); 1kW is 1,000W.
Why the real cost is usually lower than the hourly figure
The wattage on the label is what the radiator draws while its element is heating. Once the oil and the room reach the temperature you set, the thermostat cuts the power and the radiator keeps giving off stored heat. It switches back on as the room cools.
How much of the time it heats depends on the room: its size, how well it is insulated, how cold it is outside and how high you set the dial. The calculator starts at 70%, a middle-of-the-road guess for a closed, reasonably insulated room once it has warmed up. In a cold or draughty room it can be close to 100%.
To find your own figure, plug the radiator into an energy monitor, use it for an evening, then divide the kWh it shows by the radiator's kW and the hours it was on. A 2kW radiator that used 5.6 kWh over 4 hours was heating 70% of the time.
Which setting should you use?
Most oil-filled radiators have two or three power settings and a separate thermostat dial. The power setting decides how fast it heats; the thermostat decides when it stops. In a small bedroom or study, a low or middle setting with the thermostat set to a comfortable level is often enough and costs less per hour. Use full power to warm a cold room quickly, then turn it down.
As a rough guide, the bigger and colder the room, the more watts you need. A radiator that is too small for the room will run constantly and still leave it cold.
Oil-filled radiator or central heating?
Every kWh of electricity becomes a kWh of heat, so an electric heater is 100% efficient in the room it sits in. Gas is much cheaper to buy, though: 7.97p per kWh against 26.32p for electricity. Even after allowing for a boiler that wastes about a tenth of its gas, heat from central heating costs roughly 8.9p per kWh, about a third of the price of heat from a plug-in radiator.
So an oil-filled radiator saves money in one situation: when it lets you keep the central heating off while you heat only the room you are in. Running it alongside the central heating simply adds to your bill.
Five ways to cut the cost
- Use the timer to warm the room 20 to 30 minutes before you need it, instead of leaving it on all day.
- Set the thermostat to a comfortable temperature rather than the maximum. Each step down means less time heating.
- Close the door and draw the curtains so the heat stays in the room.
- Keep it away from windows and leave space around the fins so air can flow through.
- Switch to the frost or lowest setting overnight, or off, unless the room needs to stay warm.
Common questions
Are oil-filled radiators cheap to run?
Not per hour: a 2kW oil-filled radiator costs 52.6p an hour at full power, the same as any other 2kW electric heater. They can work out cheaper over an evening because the hot oil keeps giving off heat after the thermostat switches the element off, so it spends less time drawing power.
How much does it cost to run an oil-filled radiator overnight?
Eight hours at full power costs £4.21 for a 2kW model and £2.11 for a 1kW model. With the thermostat cycling at around 70% of the time, a 2kW radiator comes to about £2.95. Use a timer or the frost setting rather than leaving it on high all night.
Is it cheaper to leave an oil-filled radiator on low all day?
Only if you need the room warm all day. A lower setting uses less power per hour, but over many hours it can add up to more than heating the room for the time you are in it. A timer that warms the room shortly before you use it is usually the cheapest approach.
Do oil-filled radiators use up the oil?
No. The oil is sealed inside and is only used to hold and spread heat. It is never burned, so there is nothing to top up and no cost beyond the electricity.
Is an oil-filled radiator cheaper than central heating?
Per unit of heat, usually not. Electricity costs 26.32p per kWh, while gas costs 7.97p per kWh, or roughly 8.9p per kWh of heat from a boiler that is around 90% efficient. A radiator only saves money if it lets you leave the central heating off for the rest of the house.