Water-based or electric underfloor heating: it is not the same job.

The short answer

Water-based underfloor heating is not a heating system: it is an emitter. It needs a heat generator, a boiler or a heat pump. With a heat pump, the combination is what uses the least electricity. But it is cast in a screed: it is decided at construction, or for a renovation where everything is redone.

Thin electric underfloor heating is a complete heating system: 5 mm under the floor covering, an electrical line, one thermostat per room. It is laid on the existing floor, room by room. But every kilowatt-hour of heat is a kilowatt-hour of electricity.

We sell the second: read this page with that in mind. The rules and measurements cited come from official texts and from ADEME; the heights, weights and times, from the manufacturer of the system we fit.

The comparison

The heights, the weights, the drying, the response time and the temperature of the film come from the manufacturer of the carbon system: it is comparing its own product with the others, keep that in mind. The water temperature is the one required by the French energy savings certificate sheet. The rest comes from the texts and from ADEME, cited at the bottom of the page.

What the rules say, in France

• 28 °C in contact with the finished floor, no more. The rule dates from 1978 and applies to any underfloor heating, whatever its energy. Underfloor heating is therefore always a large warm surface.
• Water at 40 °C at most, and control driven by a sensor on the flow of each circuit: that is what the energy savings certificate sheet requires of water-based underfloor heating fitted in an existing home. It counts a standard service life of 50 years for it: that is the period used to calculate the certificates.
• Servicing for the heat generator: every year for a boiler of 4 to 400 kW, every other year for a heat pump of 4 to 70 kW. Nothing of the kind for direct electric heating.

What water-based underfloor heating does better

• Using less, with a heat pump. ADEME measured 100 houses so equipped, in twenty departments: 2.9 kWh of heat per kWh of electricity on average, more than 4 for the best set up, 1.8 for the worst. It adds that underfloor heating helps the heat pump, because it heats with water that is not very hot. The calculation method of the French energy certificate puts a figure on it: failing a known value, 3.2 for an air-to-water heat pump fitted since 2017 on underfloor heating, 2.8 on other emitters, outside the Mediterranean rim.
• Changing energy without touching the floor. The floor stays; the boiler is replaced by a heat pump when the day comes.
• Cooling. A reversible heat pump can cool the home in summer. Direct electric heating cannot.
• Qualifying for grants, in France: energy savings certificates for the floor in an existing home, MaPrimeRénov’ for the heat pump, subject to income conditions.

What thin electric underfloor heating does better

• Going on the existing floor. 5 mm under the floor covering, where a screed with its pipes needs 45 to 65: the doors, the thresholds and the staircase stay. The details are on the fitting without screed page.
• Weighing almost nothing. About 1.25 kg per m², against 90 to 130 for a screed with its pipes: on a timber floor, upstairs or on an added storey, this is often the deciding factor.
• Being quick to fit. No screed to pour or leave to dry: according to the manufacturer, one to two rooms a day, floor covering included. The sequence is on the page fitting, step by step.
• Responding quickly. Nothing to heat up before the room: the manufacturer states from 17 to 21 °C in 30 to 45 minutes. A room that is not used every day is heated when you are in it.
• Doing without a heat generator. No boiler, no outdoor unit, no plant room, no water circuit, and therefore no compulsory servicing and no possible water leak.
• Being done room by room. Each room has its own circuit and thermostat: you start with one room, and carry on when another floor needs redoing.

Which one, in which case

Rather water-based underfloor heating:

• you want to heat a whole home in Wallonia, Luxembourg or the Netherlands, or in Flanders in a renovation subject to a permit: for direct electric heating, the rule rules it out or caps it;
• you are building, or redoing everything, slab included;
• a heat pump is planned, and you are entitled to the grants;
• the home is large and needs a lot of heat: consumption is what will weigh most;
• you want cooling in summer.

Rather thin electric underfloor heating:

• you are renovating without breaking anything up, and height or weight is tight;
• there is no water circuit, and no room for a heat generator;
• you are fitting out a storey, an extension, a room, not the whole house;
• the home is well insulated: demand is low, and the purchase weighs more than consumption.

Both together: the manufacturer cites a house in Bavaria where the original geothermal system was not enough to heat the added storey. It still heats the original storeys; the new storey has its electric underfloor heating.

Doing the calculation for your home

Water-based underfloor heating is compared together with its heat generator. The page heat pump or carbon underfloor heating sets out the figures on both sides, and the simulator calculates the full annual cost with the prices in your country. The limits of electric underfloor heating are brought together on the drawbacks page.

Do you have a quote for water-based underfloor heating? Send it: we tell you what the same area would come to in 5 mm. Describe your project.

Updated on 9 October 2026.