Underfloor heating is either electric or water-based, and gas never heats a floor directly. Electric systems warm mats or films laid in the floor from an electrical circuit. A wet system runs warm water through floor pipes, and that water is heated by a gas boiler, an electric boiler or a heat pump. Choose electric if you are warming one room and the floor build-up has to stay thin; choose a gas-fired wet system if you are heating a whole floor or the whole house and a gas boiler is already there.
Electric or gas underfloor heating: what actually differs
Underfloor heating is sold in two forms: electric mats laid in the floor, and water-filled pipes fed by a boiler, which is where gas comes in. The table compares the two on the points that change the job and the running cost.
| Criterion | Electric underfloor heating | Wet underfloor heating fed by a gas boiler |
|---|---|---|
| Heat source | Electrical conductors in a mat or film warm the floor covering directly. No heating water in the system. | Warm heating water flows through floor pipes. A gas boiler, electric boiler or heat pump heats that water. |
| Working temperature | The mat heats the floor itself, so there is no flow temperature to set. | Runs at roughly 30 to 40 degrees C, against up to about 70 degrees C for radiators (Viessmann). |
| Floor build-up | Viessmann gives build-up heights from about 1.3 mm for the Vitoplanar EF3 mat, so floor levels change little. | Pipes with screed or panels add depth, so the floor usually has to be lifted or newly laid. |
| Who does the work | Electrical work. A new circuit is notifiable under Approved Document P in England. | Plumbing and heating work. Gas work on the boiler is for a Gas Safe registered engineer. |
| Controls needed | A room thermostat for the mat circuit. | Manifold, thermostatic mixing valve and temperature limiter, set and locked by a qualified heating engineer. |
| Billed at | The electricity unit rate, which Ofgem publishes separately by region. | The gas unit rate for the boiler, also published by Ofgem by region. |
Neither column is the better system in general. The deciding factors are how much floor you are heating, whether the floor is coming up anyway, and what already heats the rest of the house.
Why "gas underfloor heating" is always a wet system behind a boiler
Gas never heats a floor directly. A wet underfloor heating system is a pipe circuit filled with heating water, and the boiler warms that water. Worcester Bosch describes such a system as a low-level radiator that gives off heat by radiation and conduction through the floor. The fuel sits at the boiler, not in the floor.
Electric underfloor heating carries no heating water at all. Viessmann puts it plainly for its Vitoplanar range: unlike classic underfloor heating, the electric version has no heating water flowing through it, and electrical conductors warm the system up quickly. The mats sit under tiles, laminate or parquet and are described as maintenance-free.
A wet system can also be electrically powered, which is where the question gets muddled. The Amptec electric flow boiler heats water for radiator or underfloor heating circuits, with underfloor models working in a 30 to 60 degrees C output range. So the honest answer is: underfloor heating is electric or water-based, and gas is one of several ways to heat the water. Our guide on wet or electric underfloor heating goes through the two build types in more detail.
When electric underfloor heating is the right choice for a room
Electric underfloor heating suits a single room where floor height is tight and no wet circuit runs nearby. Typical cases are a tiled bathroom being refitted, a kitchen floor that is coming up anyway, a small extension, or a loft room far from the existing pipework.
Build-up height is often the reason it wins. Viessmann lists heights from about 1.3 mm for the Vitoplanar EF3, so thresholds and floor levels usually stay as they are. There is no water in the floor, no pump and nothing to bleed. It also fits homes with no gas supply, where one room can get its own thermostat without touching the rest of the heating.
The work itself is electrical, not plumbing. In England, a new circuit and any circuit alteration in a special location, such as the zone around a bath or shower, is notifiable under Approved Document P of the Building Regulations 2010. We do not carry out electrical work, so an electric floor is a job for a registered electrician.
When a gas-fired wet underfloor heating system is the right choice
A gas-fired wet underfloor heating system suits whole floors and whole houses where a gas boiler already heats the property. Typical cases are a ground floor being rebuilt with new screed, a rear extension joined to the existing heating, or a full central heating replacement planned from scratch.
Low flow temperature is why floors and boilers pair well. Viessmann puts underfloor heating at roughly 30 to 40 degrees C flow, against up to about 70 degrees C for radiators. Vaillant gives about 35 degrees C for a floor against about 50 degrees C for radiators, and notes that the lower the flow temperature, the more efficient the system. Viessmann also states that underfloor heating uses around 25% less energy than radiators; that is the manufacturer's own figure.
New build is a separate case. Under the Future Homes Standard consultation, fossil-fuelled heating such as gas boilers would not meet the requirement for new homes, which is why new houses often combine wet underfloor heating with a heat pump. Ideal Heating gives heat pump flow temperatures of 35 to 55 degrees C, which suits a floor circuit. If you are weighing the heat emitter rather than the fuel, see underfloor heating or radiators.
Can underfloor heating and radiators run off the same gas boiler?
Underfloor heating and radiators can share one gas boiler, but the floor circuit needs its own temperature control. Plastic pipe in a floor has to be fed through a thermostatic mixing valve that limits the circuit to around 50 degrees C, with a temperature limiter or safety cut-out as well (Worcester Bosch). Setting and locking those controls is work for a qualified heating engineer.
With a combi boiler, Viessmann advises that a suitably qualified heating engineer fits a two-way valve where radiators and underfloor heating run off one appliance. Without it the boiler can overheat and go to fault. Mixed and direct circuits are then zoned, so the floor and the radiators are called on separately.
Controls are a regulation point too. Approved Document L Volume 1 (dwellings, England) asks for room-by-room temperature control in new dwellings and when the heat generator in an existing dwelling is replaced. For wet systems in new dwellings over 150 m², it asks for at least two independently controlled circuits. Our underfloor heating page covers how we plan the circuits on a wet system.
Who may install each type of underfloor heating in England
Any work on the gas side of a wet underfloor heating system — the boiler, its gas supply or its flue — must be carried out by a Gas Safe registered engineer. HSE states that gas work by anyone not on the Gas Safe Register is illegal, and you can check an engineer's registration before work starts. Electric underfloor heating is electrical work and sits under Approved Document P instead.
If the boiler feeding a wet floor is being replaced, Boiler Plus applies in England. Since April 2018, every new gas or oil boiler in an existing English dwelling needs time and temperature control plus boiler interlock. A gas combi needs one further efficiency measure as well: flue gas heat recovery, weather compensation, load compensation, or smart controls with automation and optimisation.
As a householder you can safely check the boiler pressure gauge, the thermostat and timer settings, the reset button, and bleed a radiator. Anything inside the boiler casing, on the flue or on the gas pipework is engineer's work.
Electric or gas underfloor heating: which to choose for your home
Choose electric underfloor heating if you are warming one room, the floor build-up has to stay thin, and there is no wet circuit close enough to extend. Choose a gas-fired wet system if you are heating a whole floor or the whole house, the floor is open anyway, and a gas boiler already heats the property or is being replaced.
Running cost follows the fuel, not the floor. Electricity and gas are billed at separate unit rates and standing charges, and Ofgem publishes both by region. Compare your own tariff rather than a rule of thumb.
Before a new installation we carry out a free home survey and give you a written fixed price. If the boiler that would feed the floor is old or playing up, you can book a boiler service or repair and have its condition judged before any floor goes down.
Sources
- Worcester Bosch – The Installer's Choice (wet underfloor heating)
- Worcester Bosch – User Instructions, gas fired condensing system boiler (mixing valve and temperature limiter)
- Viessmann – Electric underfloor heating (Vitoplanar)
- Viessmann – Underfloor heating vs. radiators
- Viessmann – Can you have underfloor heating with a combi boiler?
- Vaillant – Do heat pumps work with existing radiators?
- Ideal Heating – Heat pump vs gas boiler
- Heatrae Sadia – Amptec electric flow boiler
- HSE – Domestic gas: frequently asked questions
- GOV.UK – Electrical safety: Approved Document P
- Approved Document L, Volume 1: Dwellings (2021, incorporating 2023 amendments)
- GOV.UK – Boiler Plus factsheet
- GOV.UK – The Future Homes and Buildings Standards: 2023 consultation
- Ofgem – Energy price cap unit rates and standing charges by region