A plug-in electric heater costs 26.32p for every kilowatt it draws in an hour. On full power that's 39.5p an hour for a typical 1.5 kW oil-filled radiator, 52.6p for a 2 kW fan heater and 79.0p for a 3 kW heater.
A heater with a thermostat costs less than that once the room is warm, because it switches itself on and off. The wattage and how long it's on matter much more than the type of heater.
Typical power ratings and cost per hour
Every electric room heater turns almost all the electricity it uses into heat. The Centre for Sustainable Energy (CSE) describes them as effectively 100% efficient. What differs is how many watts each type draws and how well it holds a room at temperature.
| Heater | Published rating | Typical | Cost per hour on full |
|---|---|---|---|
| Oil-filled radiator | 1,500–2,500 W (Energy Savers); typically 1.5 kW (CSE) | 1.5 kW | 39.5p – 65.8p |
| Fan heater | 1,000–3,000 W (NEA); typically 2 kW (CSE) | 2 kW | 26.3p – 79.0p |
| Electric bar fire | 2,000–3,000 W (Energy Savers); typically 2 kW (CSE) | 2 kW | 52.6p – 79.0p |
| Convector / panel heater | Typically 2 kW (CSE) | 2 kW | 52.6p |
| Halogen heater | Typically 1.2 kW (CSE) | 1.2 kW | 31.6p |
Cost per hour, evening and night by wattage
Most heaters print their rating on a plate near the plug or in the manual, and many have two or three settings (for example 750 W, 1,250 W and 2,000 W). Find your setting in the left column.
| Power | 1 hour | 4-hour evening | 8 hours overnight |
|---|---|---|---|
| 0.5 kW | 13.2p | 52.6p | £1.05 |
| 1 kW | 26.3p | £1.05 | £2.11 |
| 1.5 kW | 39.5p | £1.58 | £3.16 |
| 2 kW | 52.6p | £2.11 | £4.21 |
| 2.5 kW | 65.8p | £2.63 | £5.26 |
| 3 kW | 79.0p | £3.16 | £6.32 |
What Which?'s tests show
Which? runs each heater it tests on its highest setting in a test room. In its oil-filled radiator guide, it reports average running costs of 33p an hour for oil-filled radiators, 48p for convector heaters and 60p for fan heaters, at a then-current rate of 25.73p per kWh. We've rescaled those averages to today's 26.32p rate. Dividing by the rate also shows the average power each type drew in its tests.
| Type | Which? average per hour (at 25.73p) | Implied average power | Same heater at 26.32p |
|---|---|---|---|
| Oil-filled radiators | 33p | 1.28 kW | 33.8p |
| Convector heaters | 48p | 1.87 kW | 49.1p |
| Fan heaters | 60p | 2.33 kW | 61.4p |
The oil-filled radiators came out cheaper an hour mainly because they drew less power, not because oil is magic. Which? also found that they warmed its test room more slowly, then kept giving off heat for about half an hour after being switched off.
Worked examples
1. Heating a home office
A 1.5 kW oil-filled radiator runs from 9am to 3pm, five days a week. Once the room is warm, its thermostat keeps the element on for an estimated 60% of the time. That uses 1.5 × 6 × 0.6 = 5.4 kWh a day, which costs £1.42 a day, £7.11 a week and about £30.79 a month. With no thermostat, running flat out, it would cost £2.37 a day. The 60% figure is an illustration: the real share depends on the room, the insulation and the weather.
2. A quick warm-up before bed
A 2 kW fan heater is run for 30 minutes each night. That's 1 kWh, or 26.3p a night and about £8.01 a month.
3. A 3 kW heater all evening
Running a 3 kW heater on full for four hours uses 12 kWh, which costs £3.16. Do that every night for a 30-day month and it comes to about £94.75.
Electric heater or central heating?
On the current cap, a kWh of electricity costs 26.32p and a kWh of gas costs 7.97p (including VAT). If a gas boiler turns 90% of its gas into heat (an assumed figure for illustration), each kWh of heat from gas costs about 8.86p. Plug-in heaters therefore cost roughly three times as much per unit of heat. CSE notes that heating just one room with an oil-filled radiator can still work out cheaper if only one or two people are home and the rest of the house can stay cool. It also warns that leaving other rooms cold can lead to condensation and mould.
Ways to cut the cost
- Use the thermostat and a timer. CSE recommends both, and a plug-in time switch works for heaters without one.
- Pick the lowest setting that keeps you comfortable. Halving the wattage halves the cost an hour.
- Heat the person, not the house. An electric blanket (130–200 W, according to Energy Savers) costs 3.4p to 5.3p an hour.
- Stay safe. Plug heaters straight into a wall socket rather than an extension lead, keep them clear of curtains and bedding, and never cover them.
How we worked this out
- Price: 26.32p per kWh electricity and 7.97p per kWh gas, Ofgem price cap 1 October to 31 December 2026 (GB average, Direct Debit). Standing charges aren't included.
- Formula: cost = kW × hours × share of time on × p/kWh. Ratings come from Energy Savers, NEA and CSE.
- Which? rescaling: Which?'s average cost an hour × (26.32 ÷ 25.73). Implied power = cost an hour ÷ 25.73p.
- The thermostat percentages and the 90% boiler efficiency are illustrative assumptions and are marked as such. We haven't measured any heaters ourselves.
Frequently asked questions
Is an oil-filled radiator cheaper to run than a fan heater?
Not per kilowatt: both turn electricity into heat at the same rate, so 2 kW costs 52.6p an hour either way. Oil-filled radiators often work out cheaper in practice because they tend to have lower ratings, thermostats, and keep giving off heat after the element switches off.
How much does it cost to leave an electric heater on overnight?
Eight hours at full power costs £2.11 for a 1 kW heater, £3.16 for 1.5 kW and £4.21 for 2 kW at 26.32p/kWh. A thermostat will bring that down once the room is warm.
Are 'low-energy' or infrared heaters cheaper to run?
A heater's running cost depends on its wattage, so a 600 W heater costs 15.8p an hour whatever it's called. It gives out less heat than a 2 kW heater, too. CSE says infrared panels can suit people who sit still in draughty rooms, because they warm people and surfaces rather than the air.
Is it cheaper to heat one room with an electric heater than to put the central heating on?
It can be, if you only need one room warm for a short time. Per unit of heat, though, gas central heating is much cheaper at current prices, so for longer periods or several rooms, central heating usually wins.
Sources
All checked on 29 October 2026. Figures are restated in our own words; follow the links for the originals.
- Energy Savers (Centre for Sustainable Energy) – How much electricity am I using?: https://www.energysavers.org.uk/advice/electricity-usage/
- National Energy Action – Electricity consumption around the home (2022, PDF): https://www.nea.org.uk/wp-content/uploads/2022/03/Electricity-Consumption-Around-the-Home.pdf
- Centre for Sustainable Energy – Room heaters (reviewed January 2026): https://www.cse.org.uk/advice/room-heaters/
- Which? – Best oil filled radiators: https://www.which.co.uk/reviews/electric-heaters/article/best-electric-heaters/best-oil-filled-radiators-agOUe2W90Y1r
- Which? – Best electric heaters 2026: https://www.which.co.uk/reviews/electric-heaters/article/best-electric-heaters/best-electric-heaters-from-our-tests-aeXs65b7VHCm
- Ofgem – Energy price cap unit rates and standing charges: https://www.ofgem.gov.uk/your-energy-supply/your-energy-bill/energy-price-cap-unit-rates-and-standing-charges
- Ofgem – Changes to energy price cap between 1 October and 31 December 2026 (26 Aug 2026): https://www.ofgem.gov.uk/news/changes-energy-price-cap-between-1-october-and-31-december-2026