A heat pump water heater is a heat pump that does one job: producing domestic hot water. It is one of the only two items the highest income categories have kept in Flanders since 1 March 2026 — at the reduced amount of €450 (down from €900). In Wallonia it falls under the Primes Habitation with a mandatory prior audit. And it is the best companion to a solar installation.
How it works, and for whom
A heat pump water heater draws heat from the air — ambient air in a cellar, outdoor air, or air extracted from the ventilation system — and transfers it to a hot water cylinder. The principle is that of a heat pump, applied to domestic hot water alone.
The point is to replace a conventional electric element, which consumes one kWh of electricity to produce one kWh of heat, with a device producing several. The gain is real on an item that weighs heavily in a well-insulated house: once heating is under control, hot water becomes a significant share of the bill.
The ideal profile: a household using a lot of hot water, with a technically suitable space — cellar, utility room, sufficiently large garage — replacing an electric cylinder. Conversely, in a small flat with no dedicated space, installation is often impossible or noisy.
Solar's best ally
This is the smartest use in 2026. Since the end of the reverse-spinning meter and of solar grants, panel payback rests entirely on self-consumption: a kWh used at home is worth the full retail price of electricity, an exported kWh almost nothing.
Driving a heat pump water heater on solar surplus — running it in the middle of the day rather than at night — turns the excess into hot water instead of dumping it on the grid. It is a form of storage far cheaper than a home battery, meeting a need that exists every day anyway.
Grants by region
In Flanders, the heat pump water heater is one of the rare survivors of the 1 March 2026 tightening. Income categories 1 and 2 are left with two grants only — the heat pump and the heat pump water heater — and the latter's amount was cut from €900 to €450. Categories 3 and 4 keep access to all grants, at higher amounts. The installer must be RESCert certified.
In Wallonia, the appliance is covered by the Primes Habitation under the usual mechanism: a base amount multiplied by your income category coefficient (× 6 in R1 down to × 2 in R4), capped at 70% of the invoice including VAT in R1-R2 and 50% in R3-R4. The prior home energy audit is mandatory, and the complete file must be submitted before 30 September 2026. Check the base amount in force on the SPW Énergie portal, as it is revised regularly.
In Brussels, Renolution grants have been suspended since 1 January 2025. What remains: 6% VAT for a home older than ten years, municipal grants and the ECORENO credit.
Points to watch
- Room volume. An ambient-air unit needs a minimum volume to work — often 20 m³ or more. Installed in a cupboard, it cools the room and loses efficiency.
- Noise. The compressor is audible. Avoid mounting it against a bedroom wall.
- Cylinder sizing. Too small and the electric back-up runs constantly, wiping out the saving. Too large and you heat water needlessly.
- Installer certification. Required in Flanders, to be confirmed in writing before ordering.