United Kingdom · GBP

Electric heater running costs

Work out what a fan heater, convector or oil-filled radiator costs to run. Enter its electrical input, the hours you use it and your electricity unit rate. A thermostat can change how long the heater actually draws power.

Electric heater electricity cost calculator

Use watts and running time, or enter energy from a label, meter or completed load. Your inputs stay on this device.

What energy information do you have? Choose the information you have. Direct kWh inputs already include the cycling recorded in that energy. Electricity rate preset pence per kWh Electricity rate pence per kWh Enter 26.32 for £0.2632/kWh. Use your bill’s unit rate; standing charges are separate. Ofgem reference: 1 October–31 December 2026, Great Britain, Direct Debit, single-rate meter. Excludes Northern Ireland. Your tariff may differ.

Power and running time

Power draw watts Use measured watts or operating input power from your model’s documentation. Daily schedule hours per use day Hours in the operating window. Duty cycle accounts for cycling within that time. Duty cycle percent of scheduled time Use 100% for continuously drawn or already averaged watts. Use days per year days For seasonal use, enter your actual number of use days.

Your estimated energy cost

Scheduled hour—

Use day—

30.44 use days—

Annual total—

— across 365 use days per year

Power mode includes your selected duty cycle. The monthly figure assumes 30.44 use days; the annual total uses your selected use days. These are estimates at the entered rate.

Energy charges only. Standing or supply charges, purchase, installation and maintenance are excluded. See the calculation method and sources.

Reset calculator

JavaScript is required to update inputs and calculation methods. No total is shown until the required inputs are supplied. Cost in GBP = kWh × rate in pence per kWh ÷ 100. For power, kWh = watts ÷ 1,000 × hours × duty cycle ÷ 100. For a per-use annual estimate, multiply kWh per use by uses per active week and active weeks per year.

Before you compare costs

Use the power setting you actually run. A heater with several settings does not always draw its maximum rated watts.
The table assumes continuous power for the whole period. Time with the thermostat enabled can be longer than heating-on time.
These are appliance electricity costs. The daily standing charge is not added to each heater.

What continuous heating costs

Calculated at 26.32p/kWh. Each heater draws the stated power continuously for 1, 4 or 8 hours. These are comparison scenarios, not measured runtimes or a prediction for your room.

Example rate: Ofgem GB Direct Debit, single-rate average, 1 October–31 December 2026. The table is fixed for comparison; changing the calculator updates its results only.

What continuous heating costs
Electrical input	1 hour	4 hours	8 hours
1,000 W	£0.26	£1.05	£2.11
1,500 W	£0.39	£1.58	£3.16
2,000 W	£0.53	£2.11	£4.21

Calculate the heating-on time

Energy in kWh = watts / 1,000 x hours drawing that power. Cost in pounds = kWh x your rate in p/kWh / 100. For example, a 1,500 W heater running continuously for four hours uses 6 kWh.

If the heater draws its active power for half of an eight-hour period, use four heating-on hours, or eight hours with 50% duty cycle. Do not apply both reductions for the same off-time.

What the thermostat changes

A thermostat switches or adjusts heating to maintain a temperature. Room heat loss, weather, the chosen temperature and other heat sources affect the heating-on share. There is no single duty cycle that fits every room.

A representative kWh measurement includes the cycling that happened during that measurement. Do not multiply measured energy by a duty cycle again. If you enter average measured watts over the whole period, use 100% duty.

Is an oil-filled radiator cheaper than a fan heater?

At the same electrical draw, total heating-on time and tariff, they cost the same to run. They can deliver warmth differently, so compare the comfort and area you need to heat as well as the energy used.

A lower power setting costs less per hour while it is on, but may need to run longer for the same heating task. A thermostat or stored warmth is not a fixed percentage saving that can be applied to every home.

Common questions

How much does a 2,000 W heater cost for one hour?

At continuous full power it uses 2 kWh in one hour. At the example rate of 26.32p/kWh, that costs £0.53. Use your own tariff and actual heating-on time for your estimate.

How much does a 1,500 W heater cost for eight hours?

Eight hours at a continuous 1,500 W uses 12 kWh. At 26.32p/kWh, the example cost is £3.16. If a thermostat cycles the heater off, the energy used can be lower; the table does not assume a particular cycling pattern.

Which electric heater is cheapest to run?

For a given electricity rate, the heater that uses fewer kWh for your chosen heating task costs less. Comparing rated watts alone does not account for runtime, the area heated or the comfort you need.

Can I use the calculator in Northern Ireland?

Yes. Enter the unit rate from your own electricity tariff. The Ofgem reference covers Great Britain, so it should not be treated as a Northern Ireland rate.

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Sources and checking your inputs

Source review: 2 October 2026. Use the rate and energy units on your own tariff and product documentation. Report a correction.