Key takeaways
- Electric underfloor: £40–£120 per m² installed. Wet: £100–£190 per m²
- Electric runs at 26.11p/kWh against about 8.1p on gas and 6.5p on a heat pump
- Under roughly 10m² choose electric; over roughly 15m² choose wet
- With a heat pump, always wet: the 35–40°C flow temperature is what makes the efficiency numbers work
- Retrofit floor build-up (screed or overlay boards) is the cost most quotes leave vague
The short answer
Electric underfloor heating costs roughly £40 to £120 per m² installed and is expensive to run. Wet (water) underfloor costs roughly £100 to £190 per m² installed and is cheap to run. That trade is the whole decision.
The running-cost gap is not marginal. Electric underfloor burns electricity at 26.11p per kWh. The same heat from a gas boiler costs about 8.1p, and from a heat pump about 6.5p. Electric underfloor is therefore around three to four times the running cost of a wet system, for identical warmth.
What it costs to install
| System | Installed cost per m² | A 6m² bathroom | A 20m² kitchen-diner |
|---|---|---|---|
| Electric mat or cable | £40–£120 | £240–£720 | £800–£2,400 |
| Wet (water) pipework | £100–£190 | £600–£1,140 | £2,000–£3,800 |
Typical UK installed ranges quoted by trade cost guides, July 2026. Retrofit into an existing floor sits at the top of each range; a new screed floor during a build sits near the bottom.
Electric wins on install for two reasons: the mat is thin enough to go under tile without lifting floor levels, and a single room is a day's work rather than three. Wet systems need manifolds, pipework and usually screed, so most installers want two to four days for one room and will want to see the rest of your heating system while they are at it.
What it costs to run
Compare the fuel, not the system. Every underfloor system is close to 100% efficient at delivering heat into the room; the difference is what you pay for the heat going in.
| How it is heated | Cost per kWh of heat | Working |
|---|---|---|
| Electric mat | 26.11p | Direct electric resistance, capped unit rate |
| Wet, gas boiler | about 8.1p | 7.33p gas at roughly 90% efficiency |
| Wet, heat pump | about 6.5p | 26.11p electricity at a seasonal efficiency of 4.0 |
Put that into a real room. A 20m² kitchen with a 150W/m² electric mat draws 3kW at full output. Thermostats cycle, so assume it runs at about 40% duty over six hours on a cold day, which is 7.2kWh:
- Electric: 7.2 × 26.11p = £1.88 a day, or about £340 across a 180-day heating season
- Wet on gas: the same 7.2kWh of heat = 58p a day, or about £105 a season
- Wet on a heat pump: 47p a day, or about £84 a season
Roughly £235 a year separates electric from gas on one room. Over ten years that is well past the extra you paid to install the wet system, which is why the sizing of the room decides the technology.
Running a heat pump?
Underfloor is the ideal emitter for one, because it works at 35–40°C flow instead of the 55–65°C radiators need. Our air source heat pump guide covers flow temperatures and why they drive the whole efficiency number.
Which one for your room
The honest rule is a size threshold, and it is smaller than people expect:
- Under about 10m², or a single room off an existing system: electric. A bathroom or en-suite runs for short bursts, the running cost is small in absolute terms, and lifting the floor for pipework is disproportionate.
- Over about 15m², or a whole floor: wet. The running-cost gap compounds every winter and the install premium is a one-off.
- Any new build or full renovation with the floor already up: wet, without much argument. The cheap moment to lay pipe is when there is no floor.
- Any home with a heat pump, or planning one: wet. It is the emitter that lets the heat pump hit its efficiency numbers.
The floor build-up is the hidden cost
Retrofitting wet underfloor into an existing room usually means either digging out and re-laying a screed, or a low-profile overlay board that raises the floor by 15–25mm. Raised floors mean doors trimmed, thresholds adjusted and skirtings refitted. Get that priced into the quote rather than discovered on day two.
Is underfloor heating worth it?
For comfort, most people who fit it would not go back. Heat comes off the whole floor at a low temperature rather than off one hot panel, so the room is evenly warm at a lower thermostat setting and there is no radiator taking up wall space.
For money, it depends what you are replacing. Underfloor is not usually a saving against a well-run radiator system on the same fuel; wet underfloor's efficiency edge comes from the lower flow temperature it allows, and it is the boiler or heat pump that banks that. Where it clearly pays is as part of a heat pump install, where the low flow temperature is not a nice-to-have but the difference between a seasonal efficiency of 3 and one of 4.
Where it clearly does not pay is a large electric mat in a room you heat every day. That is the one genuine mistake in this category, and it is the most commonly sold option.
Before you price a job, check whether any of it is funded. No UK scheme funds underfloor heating as a measure in its own right, but underfloor insulation is fundable and the Boiler Upgrade Scheme's £7,500 covers a heat pump install that the pipework is often part of. The detail, and the "free underfloor heating grant" pages to ignore, is in underfloor heating grants.
Things that catch people out
- Response time. A screed floor takes hours to warm and hours to cool. You run underfloor on a schedule and a low setback, not by turning it up when you feel cold.
- Floor coverings matter. Tile and stone conduct well. Thick carpet and underlay insulate the heat you just paid for; check the tog rating before choosing.
- Insulate underneath. Without insulation below the pipes or mat, a meaningful share of the heat goes into the ground. This is not optional on a solid floor.
- You still need enough output. Underfloor delivers roughly 70 to 100W per m² in a typical build-up. A poorly insulated room can need more than the floor can give, in which case insulate the room before heating it.
Insulate first
Underfloor heating in a leaky room is expensive comfort. Our insulation payback calculator shows which measure pays back fastest on your house before you spend on emitters.
Sources
Unit rates are the Ofgem default tariff cap for 1 July to 30 September 2026, direct debit, including VAT: Ofgem price cap, July 2026. Installation cost ranges are the spread quoted by UK trade cost guides in July 2026 and vary widely by room, floor build-up and region. Correct as of 26 July 2026.