Worked examples at 26.32p per kWh
The table shows full-power costs for common heater sizes, using the Ofgem price cap average for 1 October – 31 December 2026. Your own tariff may be higher or lower.
| Heater power | 1 hour | 4 hours | 8 hours | 8 h × 120 days |
|---|---|---|---|---|
| 300 W | 7.9p | 31.6p | 63.2p | £75.80 |
| 500 W | 13.2p | 52.6p | £1.05 | £126.34 |
| 1,000 W | 26.3p | £1.05 | £2.11 | £252.67 |
| 1,500 W | 39.5p | £1.58 | £3.16 | £379.01 |
| 2,000 W | 52.6p | £2.11 | £4.21 | £505.34 |
How to work out heater running costs yourself
- Find the wattage and divide by 1,000 to get kilowatts (kW). For example, 500 W is 0.5 kW.
- Multiply by the hours you'll use it. 0.5 kW × 4 hours = 2 kWh.
- Multiply by your unit rate. 2 kWh × 26.32p = 52.6p.
Your unit rate is on your electricity bill or app, shown in pence per kWh. If you're on a standard variable tariff, the Ofgem price cap sets the maximum average rate. Fixed tariffs and Economy 7 rates differ.
How a thermostat affects the cost
The figures above assume the heater runs flat out the whole time. A heater with a thermostat can switch its element off once the room reaches the set temperature, then back on as it cools. In a small, well-insulated room that can mean it draws full power for only part of each hour. In a cold, draughty room it may run almost continuously.
Because the saving depends on your room, we don't put a number on it. A timer helps too: setting it to switch off after an hour or two stops the heater running longer than you need.
Plug-in heater vs heating the whole house
The main reason people choose a plug-in heater is to heat one room instead of the whole home. Whether that saves money depends on three things: how much of the house you'd otherwise heat, the price of gas compared with electricity, and how long you run each.
For the same amount of energy, electricity usually costs several times more per kWh than gas under the price cap. So a plug-in heater makes the most sense for short, targeted use, like a couple of hours at a desk, rather than all-day heating of a large space. If you want to compare, work out a typical day of central heating from your gas bill and compare it with the calculator above.
How to find a heater's wattage
Look on the rating label (usually on the back or underneath), in the instruction manual, or in the product listing. It's normally written as a number followed by "W", such as "500W", sometimes with a range for different settings.
The RapidHeat's wattage isn't stated in the product materials we hold, so we haven't included a RapidHeat cost figure. Ask the official store for it, then enter it above.
Running cost questions
How much does a plug-in heater cost to run?
Multiply the power in kilowatts by the hours of use and your unit rate. At the Ofgem price cap average of 26.32p per kWh (1 October – 31 December 2026), a 500 W heater costs about 13.2p an hour at full power.
Are plug-in heaters expensive to run?
It depends on wattage, hours and your tariff. A low-wattage heater used for a few hours in one room costs far less than heating a whole house, but it also gives out less heat.
Are plug-in heaters cheap to run?
They can be cheap for short, targeted use. They are not cheap if a high-wattage heater runs at full power for many hours a day. Check the numbers with your own usage.
Are plug-in heaters cheaper than central heating?
Heating only the room you're in can cost less than heating the whole home. Per unit of energy, though, electricity usually costs more than gas. Compare using your own gas and electricity rates.
How many amps does a plug-in heater use?
Divide the wattage by 230 volts. A 500 W heater draws about 2.2 A; a 2,000 W heater about 8.7 A. UK plugs are commonly fused at 13 A, which is one reason not to share a socket with other high-power appliances.
Is there a 1p-per-hour electric heater?
At 26.32p per kWh, 1p per hour means a heater drawing under 40 W at full power, which gives out very little heat. Be wary of heaters advertised this way and check the wattage.
Does a thermostat lower running costs?
A thermostat can cycle the heater off once the room reaches the set temperature, so it may draw full power for only part of the time. How much it saves depends on the room and the setting, so the calculator shows the full-power maximum.
New to this type of heater? Read are plug-in ceramic heaters any good?