Are electric radiators expensive to run? The honest answer is that it depends on three things you can work out yourself: the heater’s wattage, how long it actually heats for, and what you pay per unit of electricity. Here is the arithmetic, a cost table, and the factors that make the real figure lower than the label.
Key Takeaways
- Cost per hour at full power = wattage in kW x your price per kWh. A 1000W heater at 25p per kWh costs at most 25p an hour.
- A thermostat means the heater only draws full power while it is bringing the room up to temperature, so real costs are usually well below the maximum.
- Insulation, room size and the temperature you set matter more than the brand of heater.
- Treat any fixed “costs Xp per day” claim with caution: it cannot know your room or your tariff.
How to work out what an electric radiator costs to run
Every electric heater turns electricity into heat at close to 100 percent efficiency, so the sum is the same for all of them. Take the wattage, convert it to kilowatts (1000W is 1kW), and multiply by your unit rate.
At 25p per kWh, which is close to the current UK price cap rate, a 1000W heater running flat out uses 1kWh in an hour and costs 25p. Your own rate is printed on your bill or in your supplier app, and it is worth checking: the same heater costs 40 percent more to run at 35p than at 25p.
That 25p is the most the heater can cost in that hour. Once the room reaches the temperature you set, the thermostat cuts the power back, and from then on the heater only tops up the heat the room is losing.
Running costs by wattage
The table shows the maximum cost at 25p per kWh. Think of it as a ceiling, not a forecast.
| Heater | Max cost per hour | Max cost per 8 hour day |
|---|---|---|
| 500W | 12.5p | £1.00 |
| 750W | 18.75p | £1.50 |
| 1000W | 25p | £2.00 |
| 1500W | 37.5p | £3.00 |
| 2000W | 50p | £4.00 |
If you are unsure which wattage you need, our guide to what size electric heater you need works it out by room size.
A correctly sized heater with a good thermostat is cheaper to run than an undersized one. A heater that is too small for the room never reaches the set temperature, so it runs at full power all day.
Why the real cost is usually lower than the maximum
An electric radiator only uses full power while it is heating. In a well insulated room, once the set temperature is reached it may only need to run for part of each hour to hold it, so the hourly cost falls well below the figure in the table.
How much lower depends on how quickly the room loses heat. These are the factors that decide it:
- How well the walls, loft and windows are insulated
- The size and ceiling height of the room
- How cold it is outside
- The temperature you set, since every degree higher costs more
- Draughts and how often doors are left open
This is why two identical heaters can cost very different amounts in two different homes, and why a fixed running cost claim in an advert cannot be accurate for everyone.
Are electric radiators more expensive than gas?
Per unit of energy, mains gas is usually cheaper than electricity in the UK. But a gas boiler heats the whole house through pipework, while electric radiators heat only the rooms you use, when you use them. In homes without mains gas, flats, extensions, garden rooms and rooms used for a few hours a day, room by room electric heating can work out competitive, and it costs far less to install.
The fair comparison is the total cost of keeping the rooms you actually use warm, not the price per kWh on its own.
How to cut what you pay
- Use a heater with an accurate electronic thermostat, so it stops drawing power once the room is warm.
- Set a timer or weekly schedule so rooms are only heated when someone is there. Our smart heating controls guide explains the options.
- Lower the set temperature by a degree; it is one of the easiest savings there is.
- Close doors to rooms you are heating and deal with obvious draughts.
- Check your tariff. Time of use and off-peak tariffs can lower the cost of heating at certain hours.
For the full worked examples, including off-peak tariffs and a cost per day for every common wattage, see our electric heater running costs guide.
Final thoughts
Electric radiators are not expensive to run by nature; they cost exactly what their wattage, your tariff and your room say they will. Choose the right size, let a good thermostat and timer do the work, and heat only the rooms you are using, and the running cost stays under your control.
Heating that only runs when you need it
ADAX and Sol*Aire panel heaters with precise electronic thermostats and timers, delivered free to mainland UK.