Electricity cost calculator
What an appliance or heater costs to run, at the Ofgem price cap rate of 26.32p per kWh (1 October to 31 December 2026) or your own tariff.
How the calculation works
An appliance's power rating is in watts (W) or kilowatts (kW, 1,000 watts). Your bill charges for energy in kilowatt-hours (kWh): one kWh is one kilowatt used for one hour. So:
kWh = power in kW × hours of use
cost = kWh × unit rate
A 2 kW heater left on for 3 hours uses 6 kWh. At the current price cap rate of 26.32p per kWh, that costs £1.58. See our kilowatt-hour explainer and the kW to kWh converter for more examples.
Electric heater running costs per hour
At full power and 26.32p per kWh (1 October to 31 December 2026 price cap, paying by Direct Debit):
| Heater | Per hour | 4 hours a day for a month |
|---|---|---|
| Oil-filled radiator (1.5 kW) | 39.5p | £48.03 |
| Oil-filled radiator (2 kW) | 52.6p | £64.05 |
| Fan heater (2 kW) | 52.6p | £64.05 |
| Convector heater (2 kW) | 52.6p | £64.05 |
| Ceramic heater (1.5 kW) | 39.5p | £48.03 |
| Halogen heater (1.2 kW) | 31.6p | £38.43 |
| Infrared panel (600 W) | 15.8p | £19.21 |
| Electric blanket (100 W) | 2.6p | £3.20 |
Every plug-in electric heater turns practically all the electricity it draws into heat, so two heaters with the same wattage cost the same per hour at full power. What differs is how they deliver the heat: fan and halogen heaters warm you quickly, oil-filled radiators hold heat after they switch off, and thermostats cut the real cost once a room is warm. A heat pump is different: it moves heat from outside and can deliver several units of heat for each unit of electricity (see coefficient of performance).
Which unit rate to use
The default is the Ofgem energy price cap average for Great Britain from 1 October to 31 December 2026: 26.32p per kWh for electricity paid by Direct Debit. Electricity carries no VAT from 1 October 2026 to 31 March 2027. Rates differ by region, payment method and tariff, so type the unit rate from your bill if you know it. On time-of-use tariffs, use the rate for the hours the appliance actually runs.
Frequently asked questions
How do I work out how much an appliance costs to run?
Multiply its power in kilowatts by the hours it runs to get kilowatt-hours (kWh), then multiply by your unit rate. A 2 kW heater running for 3 hours uses 6 kWh; at 26.32p per kWh that is £1.58.
What is the cheapest electric heater to run?
Per hour, the one with the lowest wattage. Plug-in electric heaters turn practically all the electricity they use into heat, so a 2 kW oil-filled radiator and a 2 kW fan heater cost the same per hour at full power. Differences come from how the heat is delivered and how often a thermostat switches the heater off, not from efficiency.
Are oil-filled radiators cheap to run?
A 2 kW oil-filled radiator costs about 52.6p an hour at full power at the current price cap. Its thermostat cycles it on and off once the room is warm, so real hourly costs are usually lower. It is not cheaper per unit of heat than other electric heaters, but the oil keeps radiating heat after it switches off.
Are halogen heaters cheap to run?
A 1.2 kW halogen heater costs about 31.6p an hour. They warm people in front of them quickly rather than heating a whole room, which can make them cheap for short spells.
Does the calculator include the standing charge?
No. The standing charge (54.83p a day under the current cap) is paid whatever you use, so it does not change with one appliance. The calculator shows the cost of the electricity the appliance itself uses.
Is electricity cheaper at night?
Only on a time-of-use tariff such as Economy 7 or a smart tariff. On a standard single-rate tariff the price per kWh is the same at any time of day.
General information, not financial advice. Prices checked 2026-10-09 against Ofgem.