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
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.
