Sheet 08 · Heating and damp
How much does this heater cost to run?
Every electric heater costs the same to run per watt, because a watt is a watt and the meter does not care what the box says. A 2 kW fan heater flat out for an hour uses two units of electricity. So does a 2 kW oil-filled radiator, and so does a 2 kW panel with ‘eco’ printed on it. What changes the bill is how many hours it is on, and how much of that time the thermostat has it switched off.
The rate below is the Ofgem price cap unit rate for this quarter, which is what nearly everyone on a standard tariff pays. On a fixed deal, your rate is on the bill. The sheet gives you the hour, the day, the week and the month, and then tells you to buy a plug-in meter, because that is the only way to find out what the thermostat is really doing.
1Work it out
31.6p an hour while it is on, at 26.32p a kWh. £11.05 a week and £47.38 over 30 days, on top of the 54.83p a day standing charge you pay whatever you plug in.
A plug-in meter between the heater and the wall turns this estimate into a reading, and it is the only way to catch the thermostat lying.
Get a plug-in energy meter on Amazon.co.ukor search Amazon.co.uk for “plug in energy meter UK”
2The sum
Watts, divided by a thousand, times the hours it is on, times the share of that time it is actually drawing power, times the unit rate in pence. A 2 kW oil-filled radiator on for five hours with the thermostat cutting in for about six minutes in ten is 2 times 5 times 0.6, six units, and six units at the cap is what the sheet prints. The standing charge is not in it: you pay that for having a meter, heater or no heater.
3What the thermostat is worth
Flat out, a heater draws its full rating every minute. Once the room is at temperature a decent thermostat has it off more than on, and a cheap one with a dial from 1 to 6 is guessing. The three settings on the sheet are rough shares, and the sheet says so at the foot. The honest version is a plug-in meter between the heater and the socket for one evening. It costs less than the heater’s first week, and it ends the argument.
4Where it gets expensive
A fan heater left on in a room with the door open is the one that frightens people when the bill comes, not because it is a bad heater but because it never reaches the temperature where the thermostat stops it. A heated throw on your lap for the evening is pennies. A dehumidifier on its laundry setting all night is about a pound. Put each one in and see.
5When the cap changes
Ofgem resets the cap every three months and announces the January to March 2027 rate on 25 November 2026. This sheet carries the rate for the current quarter and the date it was read, both at the foot of the page, and the number moves the day the new cap starts.
6Where to get it
- Get a plug-in energy meter on Amazon.co.ukor search Amazon.co.uk for “plug in energy meter UK”Between the heater and the wall. Reads watts now and units since you plugged it in.
- Get a smart plug with energy monitoring (Tapo P110) on Amazon.co.ukor search Amazon.co.uk for “smart plug energy monitoring UK”The same reading on your phone, plus a timer, which is the bit that saves the money.
Those links go to Amazon.co.uk and earn this site a commission if you buy. The price is the same either way, and nothing on this sheet changes because of it.
7Where the numbers come from
- Energy price cap: unit rates and standing charges, Ofgem. Electricity 26.32p a kWh and 54.83p a day, direct debit, national average, 1 October to 31 December 2026 (read 17 October 2026)
- Changes to the energy price cap between 1 October and 31 December 2026, Ofgem. The January to March 2027 cap is announced on 25 November 2026 (read 17 October 2026)
- This sheet’s own rules of thumb, stated where they are used, whichfits.uk (read 17 October 2026)
Data on this sheet last changed 17 October 2026.