Choose electric underfloor heating if you are warming a single tiled room and the floor cannot rise much. Choose a water underfloor heating system if a whole floor or a new extension is to be heated by the boiler you already have. Electric mats and cables run on electricity and are an electrician's work. A water system circulates warm water from the boiler through pipes in the floor, and can be zoned room by room alongside radiators.
Electric and water underfloor heating compared: what actually differs
Electric underfloor heating runs on its own electrical circuit. A water underfloor heating system runs off the heat generator you already have, usually a gas boiler or a heat pump.
| Criterion | Electric underfloor heating | Water underfloor heating |
|---|---|---|
| What heats the floor | An electric cable or mat under the floor finish, drawing electricity | Pipes carrying warm water from your existing boiler or heat pump |
| Who carries out the work | A qualified electrician; home electrical work in England sits under Part P of the Building Regulations | A heating engineer; where the work touches gas fittings, a Gas Safe registered engineer |
| Floor build-up | Thin mats made to sit under tile and ceramic, so floor height changes very little | Pipework usually set in screed, which raises the floor and suits a new floor or extension |
| Working with radiators | Runs as its own circuit and shares no heating water with the radiators | Can share one boiler with radiators once an engineer separates the circuits with a two-port valve |
| Controls in England | Approved Document L asks for programmable room thermostats with override plus air and floor sensors on direct acting zones | Approved Document L asks for operating temperature controls, and night setback where screed is thicker than 65 mm |
| Usual scale | One room, such as a bathroom or small kitchen being retiled anyway | A whole floor or an extension, zoned room by room |
Both types run at far lower temperatures than radiators. Underfloor heating works from around 30 °C, while radiators can run up to about 70 °C. That difference shapes how each system is controlled, whichever heat source feeds it.
Which floor finishes suit underfloor heating, electric or water?
Underfloor heating can be laid under stone, ceramic, lino, vinyl, laminate, wood and even carpet. Tile and stone pass heat through best, which is why bathrooms and kitchens are common rooms for it. The finish matters more than the choice between electric and water.
- Laminate: temperatures above 27 °C can damage the boards, so the floor temperature has to be limited.
- Carpet and rugs: poor at passing heat through, so a carpeted room is a weak candidate.
- Tile, stone and ceramic: the usual pairing for thin electric mats, and they suit water pipes in screed just as well.
- Engineered wood and vinyl: workable, but the floor manufacturer's maximum surface temperature decides the design.
Tell the installer the intended floor finish before anything is designed. The finish sets the floor temperature limit, and the limit sets how much heat the room can get from the floor. A room with thick carpet planned may still need radiators, as set out in our guide on underfloor heating or radiators.
When electric underfloor heating is the right choice
Electric underfloor heating suits one room being retiled, where no heating pipework is being opened up. A bathroom refit is the classic case. The mat goes under the new tiles, the floor level barely moves, and the rest of the house carries on with radiators.
- A single tiled bathroom, cloakroom or small kitchen is being refitted anyway.
- The floor cannot rise by the depth of a screed, for example under a door that has to stay where it is.
- The room sits far from the heating manifold, so new flow and return pipes would mean lifting floors elsewhere.
- You want warm tiles underfoot rather than the main heat source for the room.
Electrical installation work in homes in England falls under Part P of the Building Regulations, and some of it is notifiable to building control. An electric underfloor system is therefore work for a qualified electrician, not for a heating engineer and not for the householder. FM Power carries out plumbing and heating work only, so an electric mat is outside what we fit.
When a water underfloor heating system is the right choice
A water underfloor heating system suits a new floor slab, an extension or a whole ground floor being refurbished, with a boiler already in the house. The pipes go in while the floor is open, then the screed goes over them. Heat comes from the appliance you already pay to run.
- An extension or loft conversion is being built and the floor is open anyway.
- The ground floor is to be underfloor heated while bedrooms upstairs keep radiators, each zone switched separately.
- A low flow temperature is wanted, because underfloor heating works from around 30 °C and also suits a heat pump later.
- A new dwelling in England with a wet heating system has a floor area of 150 m² or more, where Approved Document L asks for at least two independently controlled heating circuits.
Wet underfloor circuits are zoned, balanced and pressure-tested before the screed goes down. That testing is the point at which a buried leak is still cheap to find. Our underfloor heating page sets out how we approach that work.
What does a water underfloor heating system need at the boiler?
A water underfloor heating system needs the boiler side set up for low flow temperatures and separated circuits. Where radiators and underfloor run from the same boiler, a suitably qualified heating engineer fits a two-port valve so the boiler does not serve both at once. Without that separation the boiler can overheat and lock out.
- Plastic pipe in the underfloor circuit is limited by a thermostatic mixing valve to around 50 °C, with at least 1000 mm of copper or steel pipe at the boiler connection.
- The underfloor circuit is separated hydraulically with closely spaced tees, so the underfloor pump and the boiler pump can be considered apart.
- The maximum flow temperature comes from the boiler manufacturer's installation instructions and is set accordingly.
- System and regular boilers still need a hot water cylinder for hot water, whatever the heating circuits look like.
None of that is householder work. Across Great Britain, the Gas Safety (Installation and Use) Regulations 1998, as amended, bar anyone from working on a gas fitting unless they are competent to do so, and gas work in homes must be done by a Gas Safe registered engineer qualified for it. Mixing valves, manifold settings, boiler flow temperature, the flue and anything inside the boiler casing all sit on that side of the line.
What can you check yourself if an underfloor heating zone stays cold?
Four checks are safe for a householder when an underfloor zone or a radiator stays cold. Everything beyond them belongs to an engineer.
- Boiler pressure: read the gauge on the boiler. Cold, it typically sits around 1.5 bar. Below the marked range it is low, and repeated drops point to a leak or a faulty pressure relief valve for a Gas Safe registered engineer.
- Thermostat and programmer: check the set temperature and the on periods. Underfloor heating is designed for longer run times at low temperature, while radiators warm a room faster.
- Reset button: if the boiler shows a fault and the instructions call for it, press reset once. A fault that returns needs an engineer.
- Bleeding radiators: open the bleed key slowly anticlockwise, a quarter to half a turn, let the hiss stop and close it as soon as water appears.
More on the gauge and what the numbers mean is in our guide to low boiler pressure.
Electric or water underfloor heating: the recommendation
Pick electric underfloor heating if one tiled room is being refitted, the floor height cannot rise, and the room only needs warm tiles rather than its whole heat load covered. Pick a water underfloor heating system if a floor is open, an extension is being built, or you want a zone that runs at low temperature off the boiler you already have and sits alongside radiators elsewhere.
A free home survey settles which fits your rooms, and you get a written fixed price before any work starts. If the boiler that would feed a wet circuit is already cutting out or losing pressure, sort that first through our boiler service and repairs.
Sources
- Viessmann: Underfloor heating vs. radiators
- Viessmann: Can you have underfloor heating with a combi boiler?
- Viessmann: Is underfloor heating efficient?
- Approved Document L, Volume 1: Dwellings (2026 edition)
- Approved Document L, Volume 1: Dwellings (2021 edition incorporating 2023 amendments)
- Worcester Bosch: Installation, commissioning and servicing instructions
- Worcester Bosch Technical Bulletin TB 0137
- The Gas Safety (Installation and Use) Regulations 1998
- HSE: Domestic gas frequently asked questions
- Building Regulations Part P, electrical safety in dwellings: impact assessment
- Baxi: How to bleed a radiator in 8 easy steps
- Vaillant: Why is my boiler losing pressure?