Oil-filled radiator vs fan heater vs convector heater: running costs in the UK
Short answer: at the same power setting, an oil-filled radiator, a fan heater and a convector heater cost exactly the same to run: a 2kW heater on full costs 52.6p an hour. The real differences are how quickly you feel the heat, how well the thermostat holds the room and how long you leave it on.
Rational Picks may earn a commission if you buy through some links on this page, at no extra cost to you. See our affiliate disclosure.
Costs on this page use 26.32p per kWh (Ofgem price cap, Direct Debit, 1 October to 31 December 2026) and update automatically when the price cap changes. Data checked 11 October 2026.
Cost per hour by setting
| Heater (example model) | Setting | Cost per hour | Cost per 4-hour evening |
|---|---|---|---|
| Oil-filled radiator (De’Longhi Radia S TRRS0920) | 900W | 23.7p | 94.8p |
| Oil-filled radiator (De’Longhi Radia S TRRS0920) | 1,100W | 29.0p | £1.16 |
| Oil-filled radiator (De’Longhi Radia S TRRS0920) | 2,000W | 52.6p | £2.11 |
| Convector heater (Dimplex DXC20) | 1kW / 2kW | 26.3p / 52.6p | £1.05 / £2.11 |
| Fan heater (Dimplex DXUF20TN) | 2kW (full) | 52.6p | £2.11 |
| Any 2kW heater, thermostat on about half the time | Average 1kW | 26.3p | £1.05 |
Try your own heater and hours in the appliance running cost calculator.
Default rate: 26.32p per kWh (Ofgem price cap, Direct Debit, 1 October to 31 December 2026). Starting figures are typical values, not your model: check the rating plate or energy label and change them. Appliances with a thermostat (ovens, heaters) cycle on and off, so running at full rated power is an upper estimate. Standing charges are not included.
How we worked this out
Every plug-in electric heater turns almost all the electricity it uses into heat, so cost depends only on the power drawn and for how long. We use the power settings from each model’s spec sheet. Once the room reaches the thermostat setting, the heater switches on and off, so the average draw is usually below the maximum; the “about half the time” row is an illustration, not a measurement. See how we pick and calculate.
Which type suits what
- Fan heater: heat you feel within seconds. Best for short bursts, such as a cold bathroom or a quick warm-up. Noisier.
- Convector: warms the air in a room fairly quickly and quietly. Good for a room you use for an hour or two.
- Oil-filled radiator: slow to warm up but keeps radiating after the element switches off, giving a steady, quiet heat. Suits longer use in one room.
What changes the number
- Thermostat and timer. A heater that switches off at temperature, or on a timer, costs less than one running flat out.
- Room size and insulation. A small, well-insulated room reaches temperature sooner, so the heater cycles off more.
- Your tariff. Off-peak rates on Economy 7 or smart tariffs can make evening heating cheaper or dearer.
- Heating one room vs the whole house. A portable heater can be cheaper than central heating if you only use one room, but per kWh, electricity costs more than gas under the price cap.
FAQ
Are oil-filled radiators cheaper to run than fan heaters?
Not per hour at the same setting. Both cost the same per kWh. An oil-filled radiator can feel more even and holds heat after switching off, which can help the thermostat keep it off for longer.
Are “energy-saving” electric heaters real?
Plug-in electric heaters all convert electricity to heat at close to 100%. Savings come from better thermostats, timers and using a lower setting, not from a more efficient element.
How much does a 2kW heater cost to run per hour?
At full power, 52.6p at 26.32p per kWh. On a lower setting, or once the thermostat starts cycling, it costs less.
Is a portable heater cheaper than central heating?
It can be if you heat only one room for a short time. Heating several rooms with portable electric heaters is usually dearer than gas central heating.
Sources
- Ofgem: changes to the energy price cap, 1 October to 31 December 2026
- De’Longhi Radia S TRRS0920 oil-filled radiator: 900W / 1,100W / 2,000W settings (Currys)
- Dimplex DXC20 2kW convector heater: 1kW / 2kW settings
- Dimplex DXUF20TN upright fan heater: 2kW, two heat settings
- US Department of Energy: electric resistance heating is close to 100% efficient at converting electricity to heat
Data checked 11 October 2026.
