For a 10m² room, running flat out at full power, the maximum is 29p an hour at 28p per kWh, used as a worked example. That is the ceiling, not the bill. The thermostat cycles the heating off once the room reaches temperature, so the real figure is a fraction of it.
The calculation, in full
Take a 10m² room as the example.
When the Ribbon is being designed as the primary heat source we normally cover at least 70% of the available floor, subject to what the room actually needs. That gives 7m², which is 70% of a 10m² room.
The Ribbon produces 150W per m². Seven square metres at that output is 1,050 watts, or 1.05 kilowatts.
At 28p per kWh, used as a worked example, running continuously at full power for one hour costs 29p an hour.
That is the maximum hourly consumption for this example. It is not what you will pay every hour, and anyone quoting it as the running cost is quoting you the ceiling.
Why you never actually pay that
The thermostat only calls for heat when the room needs it.
Say you heat the room for an hour before work and three hours after you get home. That is a four-hour schedule, but it is not four hours of continuous electricity.
If the room is already at the temperature you set, the heating does not come on at all, and for that period it costs nothing. If you set it higher, the system draws power to bring the room up, then switches off once it gets there and cycles on and off to hold it.
In an average home the Ribbon draws full power for about 25% of each active hour. In a well insulated one it is nearer 7 to 10% in a well-insulated (EPC A-B) home.
What that comes to in practice
| Room | A 10m² room |
| Heated area at at least 70% coverage | 7m², which is 70% of a 10m² room |
| Load | 1,050 watts, or 1.05 kilowatts |
| Electricity price used | 28p per kWh, used as a worked example |
| Maximum, flat out for an hour | 29p an hour |
| Typical hour at a 25% duty cycle | Just over 7p for that hour |
| A four-hour schedule at that duty cycle | Around 29p for the day |
| Four hours flat out, the ceiling | About £1.18 |
| A 12m² room, average home | Around 50p a day in an average home |
Work out your own
The formula is simple enough to do on your phone. Take your heated floor area, times 150 watts per square metre, times your electricity price. That gives the maximum hourly cost.
Then apply a duty cycle. About 25% of each active hour in an average home, nearer 7 to 10% in a well-insulated (EPC A-B) home.
We are deliberately not publishing a single whole-house figure. It depends far too much on the individual property to be honest about, and a number that is wrong for your house is worse than no number at all. Per room, with the working shown, is the useful version.
Across the year
In summer it may not run at all, in spring and autumn only occasionally, and on the coldest winter days it will run for longer.
A well insulated room holds its heat longer than a poorly insulated one, so the thermostat calls for heat less often. That is why insulation and heat retention matter just as much as the price of electricity.
Solar panels and battery storage
The Ribbon runs on electricity, which means it can run on electricity you generated yourself. You cannot make your own gas.
During daylight, solar can supply the heating and cut what you buy from the grid. But most people need heat early morning and evening, when solar generation is low. A battery bridges that gap, and on the right tariff it can also charge on cheaper off-peak power.
Solar electricity is not free, the equipment has a cost and exported power has a value, but using your own generated or stored energy cuts how much heating electricity you buy at the full grid rate.
On payback, 5 to 10 years on the capital cost. That is unusual for something you buy for a house.
Is it cheaper than gas?
Here is the honest answer, and it is not the one you would expect a heating company to give.
Electricity costs more per unit than gas on a standard tariff, so it would be misleading to say electric is automatically cheaper. The comparison that matters is room-by-room control, fast response, no slab to heat, and solar, battery or off-peak on top.
Whether it works out cheaper in your house depends on how the house is built and how you live in it. That is why every job gets tested on site rather than quoted off a table.
Get the number for your actual room
The free Room Designer works out the heated area, the coverage and the price for your room, so you are not working off an example.
Running cost FAQs
How much does electric underfloor heating cost to run per hour?
For a 10m² room at at least 70% coverage the load is 1,050 watts, or 1.05 kilowatts, so at 28p per kWh, used as a worked example the maximum is 29p an hour. In practice the thermostat cycles it off, and a typical hour is just over 7p for that hour.
What does a room cost to run per day?
Around 50p a day in an average home, on unit cost alone. A four-hour schedule in the a 10m² room example is around 29p for the day.
Is electric underfloor heating cheaper than gas?
Electricity costs more per unit than gas on a standard tariff, so it would be misleading to say electric is automatically cheaper. The comparison that matters is room-by-room control, fast response, no slab to heat, and solar, battery or off-peak on top.
Does it run all the time?
No. It draws full power for about 25% of each active hour, and nearer 7 to 10% in a well-insulated (EPC A-B) home. In summer it may not run at all, in spring and autumn only occasionally, and on the coldest winter days it will run for longer.
How does solar change it?
Solar electricity is not free, the equipment has a cost and exported power has a value, but using your own generated or stored energy cuts how much heating electricity you buy at the full grid rate. Most people need heat early morning and evening, when solar generation is low. A battery bridges that gap, and on the right tariff it can also charge on cheaper off-peak power. On capital cost, 5 to 10 years on the capital cost.
What electricity price are these figures based on?
28p per kWh, used as a worked example. Substitute your own unit rate: heated floor area, times 150 watts per square metre, times your electricity price. That gives the maximum hourly cost.