Heat pump water heater: which model to choose (BE/LU)
A heat pump water heater produces domestic hot water with a built-in heat pump and uses 3 to 4 times less electricity than a standard electric tank. But between the stated COP, tank volume, air-intake type and noise, models vary widely. Here is how to pick the right one for a Belgian home.
How it works, and why it pays off
A heat pump water heater draws heat from the air with a small heat pump and transfers it to the tank water. Efficiency is read from the COP: a COP of 3 means 3 kWh of heat per 1 kWh of electricity. On domestic hot water the saving is immediate versus an electric element (COP 1).
It is often the most cost-effective step of an energy renovation: no major works, compatible with an existing installation, and paid back within a few years.
- Standard electric tank: COP ≈ 1
- Heat pump water heater: real COP 2.5 to 3.5
- Typical saving: 50 to 70 % on hot water
Which tank volume for your household
The right volume depends on the number of people and habits (bath vs shower). Too small and you run out at peak; too large and you heat water for nothing.
- 1-2 people: 100 to 150 L
- 3-4 people: 200 to 270 L
- 5 people and more: 270 to 300 L
Plan for the morning peak
A household with several back-to-back showers should aim for the higher volume: a slightly larger tank avoids the electric backup that cancels the saving.
Ambient, outdoor or extracted air
On ambient air, the unit draws air from an unheated room (cellar, utility room, garage) of at least 20 m³, well ventilated — simplest, but the room cools in winter.
On outdoor air (ducted) it takes air from outside via ducts: powerful and independent of the room, but more technical. The extracted-air version couples to the ventilation (MEV).
Noise, standardised COP and Belgian conditions
Compare COPs measured to the EN 16147 standard, otherwise the figures are not comparable. In a Belgian cellar at 10-15 °C the real COP is good; below 7 °C the unit switches to the element more often.
Noise matters if the tank is near living spaces: choose a low stated sound level and avoid placing it against a bedroom.
- COP to the same standard (EN 16147)
- Intake room > 20 m³, frost-free
- Sound level: a criterion, not a detail
Reliable brands and grants
On the Belgian market, Atlantic, Daikin, Viessmann, ACV, Vaillant and Nibe are safe choices. Favour available after-sales service and spare parts in BE/LU.
Depending on your Region, a grant can cut the bill: check the current conditions (label, minimum COP, approved installer) before buying.
Frequently asked questions
How is it different from a standard electric tank?
The electric tank heats with an element (COP 1). The heat pump water heater uses a heat pump (real COP 2.5 to 3.5) and so uses 3 to 4 times less for the same hot water.
What volume for 4 people?
Allow 200 to 270 litres for 4 people. Choose the higher volume if several showers follow each other in the morning.
Do I need a special room?
An ambient-air model needs an unheated room of at least 20 m³, well ventilated and frost-free. Outdoor-air (ducted) versions avoid that requirement but need ducts.
Is a heat pump water heater noisy?
Noise is comparable to a sturdy fridge. It only bothers near a bedroom: choose a low sound level and mind the placement.