How Much Does Underfloor Heating Cost To Run?

At the 150 W/m² default output and the 26.11 p/kWh Ofgem price cap, a 1 m² electric mat costs about 4p an hour to run; a 12 m² room (1.8 kW) costs about 47p an hour. Cost scales directly with floor area, so a 20 m² room at the same output costs roughly 78p an hour.

At the 80 W/m² default output, a 12 m² room (0.96 kW of heat) costs about 7.6p an hour on a 92%-efficient gas boiler at 7.33 p/kWh gas, or about 7p an hour on a heat pump with a 3.6 SCOP at 26.11 p/kWh electricity. Both are far below the roughly 47p an hour an electric mat costs for the same room, mainly because gas and heat-pump-multiplied electricity are cheaper per kWh of delivered heat than direct electric resistance heating.

Water-fed systems are almost always cheaper to run, in this calculator's worked example by roughly a sixth to a seventh of the electric mat's cost for the same room and schedule. Electric systems are usually chosen for installation simplicity and lower upfront cost in small rooms like bathrooms, not for running-cost efficiency.

A heat pump with a SCOP of 3.6 delivers 3.6 kWh of heat for every 1 kWh of electricity it draws, while a gas boiler at 92% efficiency delivers only 0.92 kWh of heat per kWh of gas. Whether the heat pump route ends up cheaper depends on the ratio between your electricity price and gas price - in this calculator's defaults the heat pump wins because 26.11p / 3.6 (about 7.25p per kWh of heat) undercuts 7.33p / 0.92 (about 7.97p per kWh of heat), but a higher electricity price or a better boiler efficiency could flip that.

Electric systems are typically rated at 100-200 W/m², with 150 W/m² the most common off-the-shelf spec. Water-fed systems typically deliver 60-100 W/m², with well-insulated new-builds needing as little as 50-70 W/m² and older, solid-floor properties sometimes needing 80-120 W/m².

Yes, in practice, although this calculator does not model floor covering directly. Tile and stone have low thermal resistance and let heat through efficiently, which is why they are the usual recommendation for underfloor heating. Thick carpet and underlay add resistance, which can mean the system has to run for longer, or at a higher output, to deliver the same room temperature - increasing the real-world running cost above this estimate.

The 26-week default is a general estimate for a typical UK heating season, roughly October to March. It is not drawn from a single official source and is meant to be adjusted: a well-insulated new-build in a mild region might realistically heat for fewer weeks, while an older or poorly insulated property in a colder region might heat for 30 weeks or more.

No. It only prices the electricity or gas actually used by the underfloor heating, at the Ofgem Direct Debit unit rate (26.11 p/kWh electricity, 7.33 p/kWh gas as of 1 July-30 September 2026). The daily standing charge (57.19p electricity, 29.04p gas as of the same period) is a fixed cost you pay regardless of underfloor heating use, so it is not part of a cost-to-run figure.

Industry guidance puts wet underfloor heating at roughly 25-30% cheaper to run than radiators on the same fuel, rising to around 40% cheaper when combined with a heat pump. The saving comes from the lower flow temperature underfloor systems need (35-45°C against 60-80°C for radiators), which lets a condensing boiler or heat pump run in its efficient range more of the time. This calculator does not model radiators directly; treat this as a supporting industry figure, not a page output.

Electric and water-fed systems have very different typical outputs (150 W/m² against 80 W/m²), so the calculator updates the default when you change system type. You can still overwrite the figure with your own installer's design output if you have one - the comparison table below keeps using each system's own default for the other two rows so it stays a fair like-for-like comparison.

Yes - enter your total heated floor area instead of a single room's area, and the same per-hour, per-week and per-season figures scale up linearly. Bear in mind that a whole-house heat-output figure is more likely to vary room by room than this single average W/m² model assumes.

It uses the Ofgem Direct Debit price cap, updated quarterly: 26.11 p/kWh electricity and 7.33 p/kWh gas for 1 July-30 September 2026. Overwrite both fields with your own tariff's unit rates - especially if you are on a fixed deal, a time-of-use tariff, or Economy 7 - for a more accurate figure.

Yes. Reported figures put a radiator-fed air source heat pump's seasonal performance at around 3.0-3.5, rising to 3.6-4.2 when the same heat pump feeds underfloor heating at a 35°C flow temperature, because the heat pump does not have to work as hard to reach a lower target temperature. This calculator defaults to 3.6, the conservative end of the underfloor range.

No - 92% is the minimum standard for a new UK gas boiler under the 2018 Boiler Plus rules, not a figure for an older or poorly maintained unit. Boilers installed before condensing technology became standard (pre-2005) can run well below this, sometimes in the 70-80% range, which would raise the real running cost above this calculator's gas-boiler estimate.