Hydraulic or electric underfloor heating: which should you choose?
The essentials
1. A hydraulic underfloor heating system circulates low-temperature water (30 to 45 °C) through pipes embedded in the screed. When combined with a heat pump, it heats the whole house with the best efficiency on the market and is the only one of the two systems that qualifies for Belgian grants.
2. Electric underfloor heating uses cables or mats laid just a few millimetres thick. It is quick to install, takes up almost no space and is suitable for a bathroom or a room undergoing renovation. However, electricity costs 3 to 4 times more per kWh than gas in Belgium.
3. The tipping point is the floor area. For floor areas of less than around 20 m² and for occasional use, electric heating is the better option. Above that, and for day-to-day heating, hydronic heating offers better value for money over its lifetime: 35 to 50 years, compared with 15 to 25 years for electric heating.
Two systems, two approaches
They are all grouped under the same heading, ‘underfloor heating’, but the way they work is completely different.
A hydraulic underfloor heating system is a flat-laid central heating circuit. Water heated by a heat pump, a condensing boiler or a solar system circulates through a network of PER or multilayer pipes embedded in the screed. The water circulates at a low temperature, between 30 and 45 °C, and the floor surface never exceeds 28 °C. The heat rises by radiation, without any hot spots or draughts.
Electric underfloor heating converts electricity directly into heat, through the Joule effect, via cables or mats laid beneath the floor covering. The installed power ranges from 80 to 150 W/m² depending on the room. It is available in both direct radiant and storage versions; the storage version stores heat during off-peak hours and releases it during the day.
Bear in mind the key difference: a hydraulic system requires a generator upstream and a low-temperature range to be cost-effective. An electric system simply plugs in and heats – that’s it. This simplicity is its strength in renovation projects, but its weakness when it comes to the bill.
The comparison at a glance
Hydraulic (water-based) | Electric | |
| Principle | Lukewarm water (30–45 °C) in tubes | Cables/bündels, Joule effect (80–150 W/m²) |
| Required thickness | 10–15 cm (screed) or 3–5 cm (thin-bed system) | A few mm; total 1.5 to 4 cm |
| Inertia | Advantage: takes a long time to heat up, takes a long time to cool down | Low: rapid rise and cooling |
| Compatible with heat pumps | Yes (the standard pair, SCOP 3.5 to 5) | Non |
| Installation cost (including fitting) | €40 to €100 per square metre (up to €150 for reversible flooring) | €40 to €80 per square metre |
| Cost of use | Low with a heat pump | High (electricity 3–4 times the cost of gas) |
| Service life | 35 to 50 years old | Aged 15 to 25 |
| Interview | Generator + descaling every 5–10 years | Virtually zero |
| Staying cool in summer | Possible (reversible version) | Impossible |
| Ideal for | Entire house, new build, major renovation | Bathroom, small room, additional room |
Thickness: the real deciding factor between new build and renovation
A conventional hydronic underfloor heating system requires a space of 10 to 15 cm in the floor: insulation, pipes, followed by a 6 to 8 cm screed. In new-build projects, this height is factored into the plans, so there’s no problem. In renovation projects, however, it means the floor must be raised, the bottoms of doors must be planed down, and thresholds and skirting boards must be adjusted. This is why ‘dry’ or thin-layer systems are so useful; they require just 3–5 cm and make underfloor heating a viable option in renovation projects.
Electrical wiring, on the other hand, can be fitted within a few millimetres. A mesh is glued under the tiles, followed by a levelling compound, and the whole thing remains between 1.5 and 4 cm thick. You retain your ceiling height and avoid major floor work. For a 6 m² bathroom being renovated without tearing everything out, that’s the deciding factor.
Belgian tip: When renovating a single room, first measure the available height beneath doors and at the thresholds. If you have less than 4 to 5 cm of non-adjustable space, a conventional hydronic underfloor heating system is generally not an option. In this case, you should opt for an electric underfloor heating system or a low-profile hydronic system, if the room’s layout allows.
The cost: watch out for the installation trap
The two systems are on a par when it comes to the initial purchase price. It is only with use that the gap widens.
For installation, expect to pay between €40 and €100 per square metre for a hydronic system (including fitting), excluding the boiler, and up to €150 per square metre for a top-of-the-range reversible system. Electric systems cost between €40 and €80 per square metre. For a 100-square-metre house with a hydraulic system, expect to pay between €6,000 and €9,500 all-inclusive, plus the cost of the heat pump or boiler. Based on this criterion alone, the electric option appears to be the winner. However, this is only the case if you are heating a small area.
| Facq Advice: Before choosing a system, have a thermal assessment carried out on your home. Underfloor heating – whether hydronic or electric – is pointless in a poorly insulated house: the heat escapes faster than it is generated. Insulation comes first, the heating system second. Our advisers will go through this with you at the EXPOcenter. |
Belgian subsidies and standards: where electric vehicles fall short
This is the area where the two systems are no longer comparable at all.
No regional grant funds electric underfloor heating on its own. Belgian grants support heat pumps, and therefore the associated plumbing. In Wallonia, the ‘Habitation’ grant starts at €600 for a heat pump and increases according to income, up to €3,600 for category R1. A housing audit is compulsory before work begins; air-to-air heat pumps are excluded, and the property must be over 15 years old. The transitional scheme runs until 30 September 2026; after that date, the conditions will change. In Brussels, the Renolution grant for a heat pump ranges from €4,500 to €6,500 depending on income, but it has been suspended for invoices dated 2025–2026, pending government decisions. In Flanders, the Mijn VerbouwPremie was revised with effect from 1 March 2026: €1,500 for an air-to-water heat pump (income categories 1 and 2), €4,000 for a geothermal system, with a RESCert-certified installer required. In addition, the federal VAT rate on the installation of a heat pump has been reduced to 6% until 2030, whilst the rate for gas and oil-fired boilers has risen to 21%.
Regulations are moving in the same direction. Since 1 January 2026, all new or equivalent buildings in Wallonia must incorporate at least 35 per cent renewable energy, and oil and coal-fired boilers are banned in new builds there. The combination of a heat pump and underfloor heating ticks these boxes; direct electric heating does not.
For the electrical installation in the bathroom, the RGIE applies. Since 1 March 2025, it has been aligned with the IEC 60364-7-701 standard: all circuits in the bathroom must be protected by a 30 mA residual current device (RCD), floor-recessed fittings must be earthed via an equipotential bonding, and the equipment must have a suitable protection rating (minimum IPx4 in Zone 2). When selling or letting a property, an electrical inspection by an approved body is mandatory. Nothing insurmountable, but these rules do require an installer who is familiar with them.
What sort of flooring should be laid on top?
Ceramic tiles, natural stone and polished concrete are the best heat conductors, without exception. Engineered wood flooring and vinyl or LVT are also suitable, provided they are labelled ‘underfloor heating compatible’ and the thermal resistance of the flooring remains below 0.15 m²K/W. Avoid thick carpets and underlays that are too insulating, as these trap heat in the floor. In all cases, the surface temperature must not exceed 28 °C, both for comfort and to ensure the flooring’s long-term durability.
So, which one’s for you?
The choice boils down to two questions: what size, and what purpose.
Hydronic heating is designed for new builds, major refurbishments and as the main heating system for the whole house. It becomes a viable option as soon as the floor area exceeds around 20 m² and the floor is used on a daily basis. It is the only system that can be combined with a heat pump, provide cooling in summer in its reversible mode, and qualify for government grants. Its thermal mass provides stable, comfortable heat during Belgium’s long, damp winters.
Electric underfloor heating is ideal for renovating a single room, small areas, bathrooms, hallways or walk-in wardrobes, and for providing additional comfort under tiled floors. Its slim profile and reasonable installation cost offset its running costs, provided the area remains limited. Heating a 6 m² bathroom for an hour in the morning is right up its street; heating 120 m² throughout the winter is not.
This choice between hydraulic and electric systems only makes sense once the question of the heat source has been settled: heat pump, boiler or hybrid system. If you’re still at this stage, our guide Heat pump, boiler or underfloor heating: which to choose? lays the groundwork before going into detail about the heat emitters.
In terms of equipment, Facq distributes the Biofloor (Comap) and Rolljet (Radson) hydraulic underfloor heating systems, Vaillant, Bulex and Remeha heat pumps, Bosch and Atlantic, Honeywell Home and Danfoss control systems, as well as Vasco low-temperature radiators and towel warmers, Radson and Zehnder for rooms where underfloor heating is not an option.
Frequently asked questions
Q1. Does electric underfloor heating use a lot of energy?
For a large area heated continuously, yes: electricity costs 3 to 4 times more than gas per kWh in Belgium (around €0.35/kWh compared with €0.09/kWh). It remains cost-effective for a small, well-insulated area and occasional use, such as heating a bathroom in the morning. For heating an entire house on a daily basis, a hydronic system combined with a heat pump works out much cheaper.Q2. What type of flooring should be laid over underfloor heating?
Tiles and natural stone are ideal, as they conduct heat well. Engineered wood flooring and vinyl are suitable provided they are certified as compatible with underfloor heating and their thermal resistance is less than 0.15 m²K/W. Avoid thick carpets and floor coverings that are too insulating.Q3. Is underfloor heating compatible with a heat pump?
Only the hydronic system is, and it is in fact the most efficient combination. The low water temperature (30 to 40 °C) enables the heat pump to achieve a SCOP of 3.5 to 5, which is its best efficiency. The electric underfloor heating system runs on electricity alone and is not connected to any generator.Q4. Can underfloor heating cool a room in summer?
Yes, in the reversible hydraulic version combined with a reversible heat pump: water at 15–18 °C circulates through the ground and is heated by 3 to 5 °C. A dew point sensor is then required to prevent condensation. The electric version does not cool.Q5. What power rating is required for an electric underfloor heating system in a bathroom?
The power rating is generally set between 100 and 150 W/m², as bathrooms suffer from significant heat loss. The calculation is based on the actual heatable area, excluding the bath and fixed fittings, and the installation must comply with the RGIE: 30 mA residual current device, equipotential bonding of the fittings, and a protection rating suitable for the area.