In short: underfloor heating costs whatever the heat it delivers costs. Work out the heat the room needs in kWh, then divide by how efficiently your heat source makes it and multiply by your energy price. This calculator does that for electric UFH, water UFH on a gas boiler and water UFH on a heat pump, using the Ofgem price cap figures for 1 October to 31 December 2026. You can change every figure.
Estimated running cost
How the calculator works
It uses three steps, so you can check every number.
- Heat needed per day (kWh) = floor area (m²) x heat needed while the heating is on (W/m²) x hours on per day, divided by 1,000.
- Energy bought = heat needed divided by the efficiency of the heat source. Electric UFH turns 1 kWh of electricity into 1 kWh of heat. A gas boiler at 90% needs about 1.11 kWh of gas per kWh of heat. A heat pump with a SCOP of 3.5 needs about 0.29 kWh of electricity per kWh of heat.
- Cost = energy bought x your unit price.
Heat needed while the heating is on
Once a floor is up to temperature, the heating only needs to replace the heat the room loses. The insulation options use these rough averages: 25 W/m² for a new build, 40 W/m² for a well insulated room, 55 W/m² for an average 1980s to 2000s room and 75 W/m² for an older room with little insulation. They are a starting point, not a heat loss calculation. If you know your room's heat loss, choose "Enter my own figure".
Why the heating output is not the running cost
A 150W/m² electric mat does not use 150W per m² all the time. The thermostat switches it on and off to hold the temperature, so the real draw depends on how fast the room loses heat. That is why the calculator starts from heat needed, not from the mat or pipe output.
Ways to cut the running cost
- Insulate under the heating. Cement-coated XPS tile backer board under an electric mat sends more heat up into the room and warms the floor faster.
- Use a programmable thermostat so the floor is only warm when you use the room, for example the Heatmiser neoStat-e for electric UFH.
- Keep carpet and underlay below 2.5 tog combined. Use our carpet tog calculator.
- With a heat pump, water UFH runs at low flow temperatures, which keeps the SCOP high.
Frequently asked questions
How much does electric underfloor heating cost to run?
With the default settings, a 15m² well insulated room heated for 6 hours a day needs about 3.6 kWh of heat a day. At 26.32p per kWh that is about 95p a day. Change the figures in the calculator to match your room.
Is water underfloor heating cheaper to run than electric?
Usually, yes. Gas costs far less per kWh than electricity, and a heat pump makes 3 to 4 kWh of heat from each kWh of electricity. Electric UFH is cheaper to buy and fit, so it is popular for single rooms such as bathrooms and kitchens.
Where do the energy prices come from?
The defaults are the Ofgem price cap averages for Great Britain for 1 October to 31 December 2026, paying by Direct Debit: 26.32p per kWh for electricity and 7.97p per kWh for gas. Replace them with the rates on your own bill for a closer figure.
Does the calculator include standing charges?
No. You pay standing charges whether the heating is on or not, so they are left out.