Heat pump water heater, electric or gas: the real cost

A heat pump water heater (called a "boiler thermodynamique" in French-speaking Belgium) costs 2,300 to 3,200 euros excluding VAT for a 200-litre unit installed, and cuts the consumption of an electric water heater by nearly three. Against electric, it pays for itself in about four years. Against a gas boiler that already heats your water, it does not. Here are both calculations, region by region, at October 2026 prices.

How much does a heat pump water heater cost in Belgium?

Between 2,000 and 4,500 euros excluding VAT, installation included, according to the price survey published by Trustup in July 2026. The spread comes down to two variables: the tank volume and where the unit draws its heat from.

You may also need to pay for removing the old tank (100 to 250 euros) and for a dedicated electrical circuit (150 to 350 euros), again according to Trustup. For the rest of the calculations, we take the most common case: a 200-litre monobloc at 2,750 euros excluding VAT, or about 2,900 euros if the reduced 6% VAT rate applies, which is the case for renovation work invoiced by a contractor in a home more than ten years old.

Three ways to heat water for a family of four

The table below is the heart of this article.

It compares, for the same four-person household, a conventional electric water heater, a heat pump water heater and a gas combi boiler that heats water on demand. Heat needs are set at 3,000 kWh a year for the two tanks (standby losses included) and 2,400 kWh for the combi boiler, which stores nothing. Electricity is priced at the tariff of the CREG, the federal energy regulator, for the fourth quarter of 2026 (32.25 c€/kWh in Flanders, 36.88 in Brussels, 37.79 in Wallonia), and gas at the average all-in price recorded by Selectra for October 2026 (12.11, 12.81 and 14.78 c€/kWh).

Two columns look strangely alike.

The heat pump unit and gas end up within a few tens of euros of each other in all three regions, while electric costs nearly three times as much. Everything else in this article follows from that row: the heat pump water heater is a formidable replacement for an electric water heater, and a contender with no argument against gas that is already installed.

Against an electric water heater, it pays back in four years

The saving reaches 609 euros a year in Flanders, 697 euros in Brussels and 714 euros in Wallonia. On a 2,900-euro investment, the payback period falls to 4.1 years in Wallonia, 4.2 years in Brussels and 4.8 years in Flanders without a grant. With the 450-euro Flemish grant, it drops to 4 years; with the 1,200-euro grant reserved for the lowest incomes, to 2.8 years. If your current electric water heater is reaching the end of its life, the calculation is even more favourable, since you would have paid for a new tank anyway.

Flanders has a bonus that calculators overlook. A 2.4 kW electric heating element weighs heavily in the peak power that serves as the basis for the capacity tariff (the Flemish grid charge based on your highest quarter-hour demand), whereas a heat pump unit draws about 500 W, a difference we estimated at around a hundred euros a year in our article on electric water heater consumption.

Against gas, why does the saving disappear?

Because a kWh of gas costs about three times less than a kWh of electricity, and the heat pump's coefficient of performance only just makes up for that gap. In Wallonia, the heat pump unit wins by 24 euros a year; in Flanders, by 5 euros; in Brussels, it loses 25 euros. At that rate, the 2,900 euros invested never come back.

The result is also highly sensitive to the real coefficient. Trustup reports a COP of 3.5 to 4 when the unit draws in air at 20 degrees, but only 2 to 2.5 in a cellar at 8 degrees, and a Belgian cellar in January looks more like the second case than the first. With a COP of 2, consumption rises to 1,500 kWh and the Walloon bill to 567 euros, 124 euros more than the gas boiler. Even within a single range, the gap is real: Thermor states a COP of 2.40 for its 200-litre Aéromax Access and 3.18 for its Aéromax 6 of the same volume, which means 116 euros a year of difference in Wallonia for two tanks that look alike.

Three situations do tip the balance. First: you want to leave gas altogether, because your heating is moving to a heat pump or because gas now only serves for hot water; you then save the supplier's fixed fee and the fixed grid charge, and closing the meter has its own cost, detailed in our article on opening and closing an energy meter. Second: you have solar panels, and a heat pump unit driven by your solar surplus heats water with electricity that costs you almost nothing. Third: your gas boiler is old and produces hot water at an efficiency well below our 80% assumption. To weigh up the two energies of your home more broadly, our comparison of gas or electric heating takes the reasoning further.

Ambient air, outdoor air or split: which model should you choose?

The air type decides everything else. Before comparing brands such as Atlantic, Ariston, Daikin, Thermor, Vaillant or Viessmann, all present on the Belgian market, check these six points:

• the air source: an ambient-air monobloc draws from the room it stands in, with no ducting; a ducted model draws outdoor air through two ducts; a split puts the heat pump outside, connected to the indoor tank;
• the room: for ambient air, Thermor requires an unheated, frost-free room of more than 20 m³ (garage, utility room, converted attic); a ducted model can make do with a smaller heated room;
• the COP and its conditions: compare COPs certified to the EN 16147 standard, checking the air temperature at which they were measured, 7 or 15 degrees;
• the volume: 200 litres for a household of three to five, according to Thermor's sizing table; beyond that, needless losses;
• the noise: 40 to 55 dB(A) according to Trustup, to be kept away from any bedroom;
• the controls: a unit that accepts an external signal to raise the temperature when electricity is cheap or when your panels are producing, a condition the Flemish grant actually requires.

2026 grants: only Flanders still pays

The landscape has changed three times in a year.

The Flemish conditions, published on vlaanderen.be, rule out self-installation: you need a contractor's invoice of at least 1,000 euros excluding VAT, an A+ label or better and a unit that produces domestic hot water only. In Wallonia, the Union of Walloon Cities and Municipalities confirms the end of the temporary scheme at midnight on 30 September 2026. A Walloon household that did not file its application in time therefore pays full price for its unit, unless it qualifies for the Rénopack, which targets heavier renovations.

Which drawbacks do you have to accept?

Noise, space and temperature.

One point deserves a clear answer: the storage temperature. A heat pump unit is more efficient when it heats water less, and the Belgian consumer association écoconso recommends 45 to 50 degrees. Yet below 60 degrees, a tank becomes favourable to legionella. Most units resolve this conflict with a periodic anti-legionella cycle, which raises the tank above 60 degrees using its electric element; check that it is switched on, and have the installation set up by a certified installer.

The verdict, profile by profile

All figures in this article are dated: unit prices surveyed in July 2026, electricity at the CREG tariff for the fourth quarter of 2026, gas at the average October 2026 price, grants in force on 25 October 2026. Variable offers move every month, and the gap between gas and electricity, which decides everything here, moves with them. Once the unit is chosen, the next lever is the price per kWh itself, which you can compare in our energy supplier ranking.

Sources. Installed prices, COP by air temperature, noise and installation extras: Trustup, "Boiler thermodynamique : prix en 2026", updated 6 July 2026. Electricity tariff by region: CREG, fourth-quarter 2026 tariff. Average gas price: Selectra Belgium, October 2026 prices, 17,000 kWh profile, 6% VAT included. EN 16147 certified COPs, 20 m³ room and sizing: Thermor, heat pump water heater buying guide. Recommended storage temperature: écoconso. Flemish grant: vlaanderen.be, Mijn VerbouwPremie voor warmtepompboiler. End of the Primes Habitation: UVCW, 20 May 2026; Rénopack and Rénoprêt: SWCS and Belgian Official Gazette of 30 September 2026. Brussels situation: public surveys of Renolution grants, July to October 2026. Pages consulted on 25 October 2026. Annual costs and payback periods are estimates based on these sources, with a real COP of 2.7 and a boiler efficiency of 80% assumed by us.

Camille