Space Heater Running Cost: What a 1–3 kW Heater Really Costs (and How to Control It Safely)

A space heater's running cost is its power in kilowatts multiplied by the hours it runs and your price per kWh. At full power a 1 kW heater uses 1 kWh an hour, a 2 kW heater 2 kWh and a 3 kW heater 3 kWh. At the UK price cap rate for October to December 2026 (about 26.32p per kWh), that's roughly 26p, 53p and 79p an hour; at the EU average of around €0.28 per kWh, it's about 28, 56 and 84 cents. Because the thermostat switches the element on and off, the real cost is usually lower than these full-power figures, and measuring tells you by how much.

Running costs at a glance

The table assumes the heater runs at full power the whole time, which is a worst case. UK prices use Ofgem's average direct debit unit rate of 26.32p per kWh for 1 October to 31 December 2026 (it varies by region and payment method); EU prices use the first-half 2026 Eurostat average of around €0.28 per kWh, as reported by the Brussels Times.

Prices differ widely by country. In Germany, at around €0.36 per kWh in the same Eurostat period, a 2 kW heater at full power for 4 hours a day would cost about €2.88 a day or €86.40 over 30 days. Use the unit rate on your own bill.

How to work it out yourself

1. Find the heater's maximum power on its rating plate, in watts or kilowatts. Many heaters have two or three settings (for example 1 kW / 2 kW).
2. Convert to kWh: kW × hours. A 2 kW heater for 3 hours = 6 kWh.
3. Multiply by your unit rate: 6 kWh × 26.32p = £1.58, or 6 × €0.28 = €1.68.

The full method, with other appliances, is in our guide to calculating an appliance's running cost.

Why the real cost is usually lower (and how to find it)

A heater with a thermostat heats until the room reaches the set temperature, then cycles the element off and on to hold it. So a "2 kW" heater might average much less over an evening, depending on the room, insulation, outside temperature and setting.

Hypothetical example: you run a 2 kW heater for a 4-hour evening and an energy monitor records 5 kWh. The average draw was 5 ÷ 4 = 1.25 kW. The evening cost 5 × 26.32p = £1.32, or 5 × €0.28 = €1.40, rather than the full-power £2.11 or €2.24.

That gap is why measuring is worthwhile. A plug-in energy meter or an energy-monitoring smart plug records actual kWh; see how to measure appliance energy use for the options.

Does the type of heater change the cost?

Fan heaters, convector heaters, oil-filled radiators and panel heaters all turn essentially all the electricity they draw into heat. So per kWh, they cost the same. What differs is how the heat reaches you (fan heaters warm air quickly; oil-filled radiators release heat slowly) and how well the thermostat and your habits cut run time. The lever that matters most is hours at power, not heater type.

Safety first: heaters and smart plugs

Heaters are among the highest continuous loads in a home. Before you put any timer or smart plug between a heater and the wall, go through this checklist.

1. Read the heater's manual first. Many heater manuals include a warning that the heater must not be supplied through an external switching device such as a timer, because a thermal cut-out could be reset unexpectedly. If your manual says this, do not use a smart plug or plug-in timer with that heater. Use its built-in thermostat and timer instead.
2. Check whether the manual says to plug directly into a wall socket. Many do. If yours does, follow it.
3. Match the plug's rating to the heater's maximum wattage, with headroom.
   • EU 16 A plug: 16 A × 230 V ≈ 3,680 W maximum.
   • EU 20 A plug: 20 A × 230 V ≈ 4,600 W maximum. The extra rating is headroom for the plug only. A standard Schuko wall socket is typically rated 16 A, so the socket and its circuit remain the limit.
   • UK 13 A plug: 13 A × 230 V ≈ 2,990 W maximum. A 3 kW heater runs right at that limit with no headroom, so it's a poor match for any plug-in smart plug. Choose a heater whose maximum rating sits comfortably below 13 A.
4. Never daisy-chain. No smart plug into an extension lead, no adaptor into a smart plug, no heater on a multi-way strip. Smart plug straight into the wall socket, heater straight into the smart plug.
5. Don't use extension leads for heaters at all. Electrical safety advice in the UK is to plug portable heaters directly into a wall socket, because extension leads can overheat under sustained high loads.
6. Keep clearance. West Sussex Fire and Rescue Service advises keeping portable heaters at least a metre from anything combustible, standing them on a level surface where they can't be knocked over, and not leaving them unattended or on while you sleep. Its heating appliance safety advice is worth a read.
7. Check plugs and sockets for heat. If a plug, smart plug or socket feels hot, smells or shows discolouration, switch off and stop using that combination.
8. Don't rely on overload protection. An automatic shut-off is a last line of defence, not a substitute for staying within the rating.

Using timers and schedules sensibly

If your heater's manual allows external switching and the plug rating fits, the safest uses are about switching off:

• Countdown timer. Set the heater to switch off after, say, 45 minutes so it can't run all evening by accident.
• Bedtime schedule. Cut power at a fixed time every night, as a backstop if you forget.
• Remote off. If you've left the house and the app shows the heater drawing power, turn it off.

Switching a heater on remotely or by schedule is a different matter. Fire services advise not leaving heaters unattended, so only do it if the manual allows it, the heater is in a clear, stable spot and someone will be in the room soon. Never schedule a heater to come on in an empty home.

Ways to cut space heater costs

• Heat the room you're in, for the hours you're in it, and keep the door closed.
• Use the lowest setting that works. On a 1 kW / 2 kW heater, the lower setting halves the maximum hourly cost.
• Set the thermostat a little lower and use the heater's own timer where it has one.
• Draught-proof gaps around doors and windows so heat stays in.
• Measure a typical evening, change one thing (setting, hours, door closed), and measure again.

Common mistakes

• Assuming the label wattage is what you pay for. It's the maximum.
• Running a heater through an extension lead or adaptor. Plug it into the wall.
• Choosing a smart plug by plug shape, not rating. Check amps against the heater's maximum.
• Treating a 20 A smart plug as permission to exceed the socket. The wall socket and circuit still set the limit.
• Ignoring the manual's warning about timers. If it's there, it applies to smart plugs too.

Where Wattly fits (and where it doesn't)

The Wattly smart plug shows a heater's live watts and its cost per hour, day, week or month, with usage history, so you can see what your evenings actually cost. It comes in EU Type F (Schuko) versions rated 16 A (3,680 W max) or 20 A (4,600 W max), and a UK Type G version rated 13 A, with overload protection and a physical on/off button. Countdown timers, schedules and remote off cover the safer timer uses above.

It is only suitable if your heater's manual allows external switching and the heater's maximum wattage sits comfortably within the plug's rating, with the plug going straight into a wall socket. If your manual forbids timers, or you have a 3 kW heater in the UK, use the heater's own controls instead. You can see the Wattly smart plug and current price, and for more ideas on what to automate (and what not to), read smart plug ideas and schedules.

Related reading

• Smart plug with energy monitoring explained
• How to reduce your electricity bill in the UK
• What uses the most electricity at home