Heated throw against central heating, what an evening on the sofa costs
Dreamland publishes an energy use of 301 watt hours over an eight hour session for its Relaxwell heated throw, an average of 38 watts, so a three hour evening costs about 3p at the Ofgem cap rate of 26.11p per kWh. Three hours of gas central heating with the boiler modulating at 10 kilowatts costs roughly £2.20, which is why the throw is the cheapest warm thing in the house.
What a heated throw actually uses
Most pages on this subject take the rating printed on the controller, usually 120 or 150 watts, multiply it by the hours and publish a number three or four times too large.
Dreamland does something more useful with the Relaxwell throw. It publishes measured energy use, 301 watt hours over an eight hour session, based on five minutes heating at maximum and then dropping to setting three. That works out at an average of 38 watts across the whole session, because the element spends most of its time switched off while the fleece and your own body heat hold the temperature.
We use 38 watts as the everyday figure and 150 watts as the worst case for a throw held on maximum with no cycling at all.
Work it out for your own heated throw
Type in the wattage from the plate on the back, then your own unit rate. The numbers update as you type.
Three hours on the sofa, five different ways
| How you keep warm | Power | Three hour evening | Month of evenings | Winter of 180 evenings |
|---|---|---|---|---|
| Heated throw, measured average | 38 W | 3.0p | 89p | £5.36 |
| Heated throw held on maximum | 150 W | 11.8p | £3.52 | £21.14 |
| Electric underblanket on the sofa | 70 W | 5.5p | £1.64 | £9.87 |
| 2kW plug in heater for the room | 2,000 W | £1.57 | £47.00 | £281.99 |
| Gas central heating at 10kW output | 10,000 W | £2.20 | £65.97 | £395.82 |
The gap between the top row and the bottom row is not a rounding difference. It is the difference between heating a person and heating a building, and it is why a five pound throw bought in October pays for itself in the first week of November.
| Appliance | Typical draw | Usage we assume | Per hour (UK) | Per usage (UK) | Per month (UK) | Per hour (US) |
|---|---|---|---|---|---|---|
| Heated throw | 38 W | per 3 hour evening | 0.99p | 3.0p | 90.3p | 0.70 cents |
Rates: Ofgem cap 1 July to 30 September 2026 at 26.11p per kWh (source), EIA residential average June 2026 at 18.34 cents per kWh (source). Checked 2026-09-22.
How the two sums work
The throw is the easy one. Dreamland's 301 watt hours over eight hours is 0.301 kilowatt hours, which at 26.11p is 7.9p for the full session and about 1p an hour. Three hours comes to 3p.
Central heating takes one assumption, which is how hard the boiler works. A modern combi modulates between roughly 5 and 24 kilowatts, and a typical three bedroom house in November settles somewhere near 10 kilowatts while it is bringing the place up to temperature, then less once it is there. Ten kilowatt hours of gas at 7.33p is 73.3p an hour, so three hours is £2.20. If your boiler runs nearer 6 kilowatts the figure drops to £1.32, which is still more than forty times the throw.
Using both together, which is the point
- Drop the thermostat by two degrees and hand everybody a throw. That combination saves far more than either move on its own, because the boiler runs for shorter cycles rather than at a lower output.
- Heat the room you are in and let the throw cover the gap in the evening, rather than heating the whole house to a level that makes sitting still comfortable.
- Set the heating to come on an hour before bed rather than running it all evening, since the throw covers the sofa hours and the house only needs enough warmth for moving about.
- Keep the throw for sitting still. It works by trapping heat, so it does almost nothing for someone walking between rooms, and it is no help at all in a kitchen.
- Wash it on the cool setting and dry it flat. A throw whose wiring has been stretched in a tumble dryer is the one failure mode worth avoiding, and replacement costs more than several winters of running.
Where the throw is the wrong answer
Second guessing this properly matters, because the arithmetic is so lopsided that it tempts people into turning the heating off altogether.
A house held below about 14 degrees starts collecting condensation on cold surfaces, and condensation turns into mould on the wall behind the wardrobe rather than anywhere you would notice early. Cold plumbing in an unheated loft or garage is a burst pipe waiting for the first hard frost. Anybody elderly, very young or with a respiratory condition needs ambient warmth rather than a warm lap.
The throw lets you set the thermostat to 17 or 18 instead of 21, which is a genuine saving of a few hundred pounds across a winter. It does not let you set it to off, and any page telling you otherwise has done the electricity sum without doing the building one.
What to look for if you are buying one
The running cost barely varies between models, so buy on the things that decide whether it gets used every evening or ends up folded in a cupboard.
Size is the first one, since a 160 by 120 centimetre throw covers one adult properly and a smaller one leaves your feet out. A timer matters more than the number of heat settings, because the common failure is falling asleep under it and waking at 2am with it still on. Overheat protection and a detachable controller are worth insisting on, and both are standard on anything from an established brand.
Machine washability decides how long you keep it. A throw that has to go to a dry cleaner after a spilled cup of tea stops being used within a month, and the cheapest heated throw in the house is the one you already own and actually reach for.
What this costs in the United States
At the EIA residential average of 18.34 cents per kilowatt hour, an eight hour session with the throw costs 5.5 cents and a three hour evening costs 2.1 cents. A full winter of 180 evenings comes to $3.76. Americans heating with natural gas face a similar ratio to the British one, and those on electric resistance heating face a far larger one, since a 1500 watt space heater for three hours costs 83 cents against two cents for the throw.
Common questions
Do heated throws use a lot of electricity?
No, they use about as much as a laptop. Dreamland's own figure of 301 watt hours over eight hours works out at 38 watts on average, which is 1p an hour. Even held at its full 150 watt output the throw only costs 3.9p an hour.
How much does it cost to run a heated throw for an hour?
About 1p an hour at the average draw and 3.9p an hour if it never cycles off. A three hour evening therefore lands between 3p and 12p depending on the setting, the room temperature and whether you are sitting under it or on top of it.
Is it cheaper to use a heated throw than central heating?
Dramatically, for one or two people in one room. A month of evenings under the throw costs about 90p and a month of three hour heating sessions costs about £66. The throw does not protect the house from damp or cold plumbing though, so it lowers the thermostat rather than replacing it.
How much does it cost to run a heated throw all day?
Eight hours costs 301 watt hours by Dreamland's measurement, or 7.9p. A full waking day of 16 hours comes to around 16p, which is still less than one hour of a 2 kilowatt plug in heater.