What does an electric heater actually cost to run in the UK?

The formula, in ten seconds

Cost per hour = kilowatts × your electricity unit rate.

Your unit rate is printed on your energy bill in pence per kWh, and it varies by region, tariff and meter type. Your heater's wattage is on its label or in the manual — divide watts by 1,000 to get kilowatts. So a 1,200 W heater is 1.2 kW, and at 27p per kWh it costs 1.2 × 27 = about 32p an hour at full power. For a day, multiply by the hours you actually run it.

Running cost calculator

Cost per hour by wattage at 27p per kWh

The table uses an illustrative 27p per kWh. Substitute your own rate — every figure scales directly with it. The last column is an illustrative 60% run-time scenario, not a prediction: actual thermostat cycling depends on room size, insulation, weather and setting.

Electricity prices move with the price cap and with your tariff, so always check your own bill rather than relying on a figure you read online — including this one.

Want a quick answer? See how much a 2kW heater costs to run or electric heating cost per month.

Why the headline figure overstates the real cost

That first column assumes the heater runs flat out for the whole hour. A heater with a thermostat may not. It draws full power until the room reaches your set temperature, then cycles the element off and on to hold it. The actual duty cycle varies with insulation, outside temperature, room size, draughts and the chosen temperature, so there is no honest universal percentage saving.

This is the single most important thing to understand about electric heating costs, and it is why a thermostat and a timer matter far more than the wattage on the box.

A 1.2 kW plug-in heater draws about the same as a small kettle — the difference is that a kettle runs for three minutes and a heater can run for hours. Hours, not watts, decide your bill.

Electric heater vs central heating for one room

Gas costs roughly a quarter of what electricity costs per unit of energy, so heating a whole house with electric heaters would be expensive. But that is not the comparison most people are actually making. The real comparison is:

• Option A: fire up the boiler and warm every radiator in the house so one room becomes comfortable.
• Option B: heat only the one room you are sitting in.

If you are working from home in one room, or in a bedroom in the evening, Option B often wins on cost simply because you are heating a fraction of the volume. Once you need three or four rooms warm at the same time, the boiler wins again. Whether it does in your home depends on your boiler, tariff, insulation and how many rooms you use — the full comparison is in electric heater vs central heating.

Six ways to cut the cost without being cold

1. Use the thermostat properly. Set the temperature you actually want, not the maximum. Turning it to 28°C does not warm the room any faster — it just overshoots and costs more.
2. Use the timer. Warm the bathroom for 20 minutes before a shower rather than leaving a heater on for three hours, and heat the first hour of the morning and the last hour of the evening only.
3. Close the door and block the draughts. A closed door roughly halves the volume you are heating, and a £5 draught excluder does more for a cold room than a more powerful heater.
4. Close the curtains at dusk. Glass loses heat faster than any wall in the house.
5. Use the lower power setting to hold temperature. Reaching temperature slightly slower on 800 W costs less than blasting 1,500 W and then opening a window.
6. Right-size the heater to the room. A heater fighting a room that is too big for it never reaches its set point, so it never cycles off — see how to size a heater for your room.

Economy 7 and time-of-use tariffs

If you are on Economy 7, Economy 10 or a time-of-use tariff, you have two very different unit rates and the cheap window is usually overnight. That changes the sums in two ways:

• Heating during the cheap window can cost less than half the day rate — worth knowing if you want the bathroom warm first thing.
• Your peak-rate hours can be well above the 27p used here, so run the calculator with your actual day rate before deciding an evening in a warm room is cheap.

A plug-in heater cannot store heat, so it cannot shift an evening's heating into the cheap window the way a storage heater does. Check your cheap-rate hours on your bill or in your supplier's app, then decide when to heat.

What about standby and "eco" claims?

A heater on standby draws a fraction of a watt — irrelevant to your bill. Be sceptical of any product claiming to use less electricity than another for the same amount of heat: every electric heater converts essentially all of the electricity it draws into heat, so a 1.2 kW heater from any brand costs the same per hour at full power. The only real savings come from lower power, fewer hours and a smaller space. Anyone telling you otherwise is selling you something.

What RapidHeat costs to run

RapidHeat runs at up to 1,200 W, so at 27p per kWh that is about 32p an hour while the element runs. An illustrative 60% run-time scenario would be about 19p per clock hour, or around £17.50 a month at three hours a day; your room may be higher or lower. It is built for exactly the case above: a warm room in about five minutes, an adjustable thermostat that cycles instead of running non-stop, and a timer so you only pay for the window you need.

£49.95 for one · £110.89 for three (about £36.96 each)

Free tracked UK delivery and a 30-day money-back guarantee, so you can test the running cost in your own room against your own bill.

Choose your bundle

Next: the cheapest way to heat a single room and how to choose a plug-in heater.