Glossary · Central heating, radiators and hot water
Wet vs electric underfloor heating: what is the difference?
Wet underfloor heating circulates warm water through pipes under the floor, fed by a boiler or heat pump. Electric underfloor heating warms the floor with electric cables or mats. Wet systems cost more to fit and suit whole rooms. Electric systems are thinner and quicker to install, and suit a bathroom or kitchen.
Key points
- Wet systems run on a low flow temperature, around 35 to 45°C according to BASI, which suits heat pumps and condensing boilers.
- Low-profile wet pipe systems add about 15 to 20mm to the floor. Electric mat under tile adds about 3 to 5mm, BASI says.
- BASI says electric mat is cheap, fast and well suited to a bathroom or kitchen retrofit where you are tiling anyway.
- BASI says wet systems cost more to fit but a fraction to run, and shine when heating a whole room continuously.
- Approved Document L expects any new underfloor system to have controls to adjust its operating temperature.
How the two systems work
A wet (warm-water) system lays pipe in or over the floor and circulates warm water from the boiler or heat pump. An electric system uses heating cable or mats that warm up when mains power passes through them. Both turn the floor into a large, gentle heat emitter, so no radiator is needed in the heated area.
BASI offers both. It says electric mat under tile is cheap, fast and a good choice for a bathroom or kitchen retrofit where you are tiling anyway. It says wet systems cost more to fit but a fraction to run, and are best when heating a whole room continuously or pairing with a heat pump.[1]BASI Heating, Underfloor heating
Side by side
| Wet | Electric | |
|---|---|---|
| Heat source | Boiler or heat pump | Mains electricity |
| Flow temperature | Low, around 35 to 45°C | Not applicable |
| Floor build-up (low-profile retrofit) | About 15 to 20mm | About 3 to 5mm for mat under tile |
| Installation | Costs more to fit | Cheap and fast |
| Best suited to | Whole rooms heated continuously, heat pump homes | Bathrooms and kitchens |
A wet system’s low flow temperature is why it pairs well with an air to water heat pump. It can also run from a modern condensing boiler through a mixer manifold, so radiators elsewhere keep their own temperature.[1]BASI Heating, Underfloor heating
What the building regulations say
Approved Document L, for England, says any new underfloor system should have controls to adjust the operating temperature, and the standards for room thermostats apply to underfloor heating.[2]Ministry of Housing, Communities and Local Government, Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments For electric systems it adds that room thermostats should have a manual override, that cables in screeds on direct electric systems should be in screeds not exceeding 60mm, and that programmable room thermostats with an override should serve direct electric zones.[2]Ministry of Housing, Communities and Local Government, Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments Floors should also be insulated to limit heat lost downwards.[2]Ministry of Housing, Communities and Local Government, Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments
The pipework and boiler or heat pump side of a wet system, and the mains wiring of an electric one, are work for qualified people. Gas work needs a Gas Safe registered engineer, and electrical connections need a qualified electrician.
Example
Hannah is retiling a Bradford bathroom and wants a warm floor. Her installer suggests electric mat, because the floor is being tiled anyway and the added height is small. Next door, Tom is building an extension and plans a whole-room floor on a heat pump, so a wet system suits him.
What people get wrong
People often assume underfloor heating means digging up the floor. For most retrofits it does not, as the low-profile systems sit over the existing subfloor.
Another common idea is that one type is better. BASI says it does not push one over the other. It surveys the room, the floor build-up and the heat source, then quotes what makes sense.[1]BASI Heating, Underfloor heating BASI lists underfloor heating from £700 at a fixed price.[1]BASI Heating, Underfloor heating
The bottom line
Electric is thin, quick and well suited to a single bathroom or kitchen. Wet costs more to install and suits larger, continuously heated rooms or a heat pump. A survey of the floor and your heat source decides which fits your home.
Common questions
Is wet or electric underfloor heating cheaper?
BASI says electric mat is cheap and fast to fit, while wet systems cost more to fit but a fraction to run. Which is cheaper overall depends on the room, how long it is heated and the fuel.
Do I have to dig up the floor for underfloor heating?
For most retrofits, no. BASI says low-profile pipe systems lay over the existing subfloor and add 15 to 20mm, and electric mat under tile adds about 3 to 5mm. A screed pour is mainly for extensions or full renovations.
Does underfloor heating need a thermostat?
Yes, in effect. Approved Document L says new underfloor systems should have controls to adjust the operating temperature, and room thermostats for electric systems should have a manual override.
Can underfloor heating work with a heat pump?
Yes. BASI says wet underfloor heating wants a low flow temperature of around 35 to 45°C, which makes it a natural match for an air source heat pump.
Sources
We cite the original source for every figure: government, regulators, standards bodies and manufacturers' own documents. Each one shows the date we last checked it.
- BASI Heating. Underfloor heating. Checked 11 November 2026. ↩
- Ministry of Housing, Communities and Local Government. Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments. Checked 11 November 2026. ↩