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Pierre M.Tournai
Solar thermal · Solar water heater
Solar water heater: your hot water heated for free by the sun
The individual solar water heater (SDHW) captures the sun’s heat with thermal collectors, transfers it to a heat-transfer fluid, then to a tank via an exchanger. In Belgium, it covers 50 to 65% of your hot water needs over the year. The backup takes over in winter — you pay nothing for the sun.
- 4–6 m²
- of typical collectors
- 200–300 L
- solar tank
- 20+ years
- lifespan
50–65%solar hot water/year
Dedicated tankwith built-in exchanger
Technical specifications
What a solar water heater is really worth
The figures that matter for a well-sized SDHW under the Belgian climate. Concrete benchmarks, not marketing.
- Type of collectors Flat or tubes
Flat collectors, robust and economical, suit most roofs. Evacuated tubes, more efficient in low sunlight and cold, capture the Belgian winter better — at a higher cost.
- Coverage rate 50–65% over the year
Over an average year in Belgium, solar covers 50 to 65% of domestic hot water needs: nearly 100% in summer, far less in winter. Hence the indispensable backup during the dark months.
- Tank volume 200–300 L
The solar tank with exchanger is sized to the household’s consumption: about 50 litres per person. Too small, it stores the summer surplus poorly; too large, the backup works too hard.
- Collector surface 4–6 m²
For a household of 4, count on 4 to 6 m² of collectors facing south, tilted at 35–45°. The surface is matched to the tank volume to avoid summer overheating.
- Backup Indispensable
The Belgian winter is not enough: a backup (electric element, boiler or heat pump) tops up the tank when the sun falls short. It is what guarantees hot water all year round.
- Fluid & pump Glycol + pump
An antifreeze water-glycol mix circulates in a closed loop between the collectors and the exchanger, driven by a controlled pump. A regulator stops the pump when the tank is warmer than the collectors.
* Indicative values for a standard domestic SDHW. The exact sizing (collectors, tank, backup) depends on your consumption and your roof — confirmed during the study.
In full transparency
Pros & cons of the solar water heater
No solution is perfect for every household. Here, honestly, is where the SDHW excels and where you should look elsewhere.
Where it shines
- 100% free energyThe sun heats your water with no bill: 50 to 65% of needs covered over the year.
- Very low footprintNo combustion or electricity for the solar share: lasting CO₂ savings.
- Proven technologyReliable collectors and tanks, over 20 years’ lifespan with minimal maintenance.
- Subsidies availableWallonia and Brussels support the SDHW, which clearly shortens the payback period.
What to keep in mind
- Backup mandatory in winterSolar alone is not enough from November to February: a backup remains indispensable.
- Covers hot water, not heatingAn SDHW targets domestic hot water; to heat the home, that is another system.
- Initial investmentMore expensive to buy than a simple water heater, even if subsidies narrow the gap.
- Circuit maintenanceThe glycol and the pump require periodic checks to keep the output up.
For which project
Is the solar water heater right for you?
It comes into its own as soon as hot water use is regular and the roof is well exposed. A few cases where it shines:
-
Family with high demand
The more hot water the household uses (showers, baths, dishes), the more profitable the SDHW. This is the ideal case of a home with 3 to 5 people.
-
Well-oriented roof
A clear roof facing south (or south-east/south-west), tilted around 35–45°, gives the best solar coverage rate over the year.
-
Energy renovation
When replacing an old electric water heater, switching to solar slashes the hot-water bill and captures the regional subsidies.
No guaranteed sun, or little roof space?
If sunlight or roof space is limited, the heat-pump water heater (a heat pump on the air, not solar) heats the water all year. And to produce your electricity, see solar panels.
Glissez la poignée pour comparer
Real case · 4-person house, Namur
An electric water heater replaced by a 4.5 m² SDHW
A Namur family was paying a heavy hot-water bill on an old electric water heater. We fitted 4.5 m² of south-facing flat collectors and a 300 L solar tank with exchanger, with electric backup. The result: most of the hot water is now solar, with the backup working only during the dark months.
- 62%solar hot water/year
- 300 Lsolar tank
- −55%on the DHW bill
Customer reviews
They chose wendows
5.0/5 · 1verified reviews
Compare the options
Solar water heater, or something else?
The SDHW wins on free energy and carbon footprint. Compare it point by point with the heat-pump model and overall solar thermal, then open the solution that interests you.
| Critère | Solar water heaterVous êtes ici | Heat-pump water heaterVoir la gamme → | Solar thermalVoir la gamme → |
|---|---|---|---|
| Energy source | Sun (free) | Air + electricity | Sun (free) |
| Hot-water coverage | 50–65% solar | Nearly 100% all year | 50–65% solar |
| Backup needed | Yes, in winter | No (self-sufficient) | Yes, in winter |
| Carbon footprint | The lowest | Low with green electricity | The lowest |
| Indicative price | €€€ — collectors + tank | €€ — more accessible | €€€€ — full system |
| Roof space | 4–6 m² needed | None | Large surface |
| Ideal for | South roof, high DHW use | Little sun or space | DHW + solar heating |
Indicative benchmarks for mainstream installations. The right choice depends on your roof, your consumption and your budget — we refine it together during the study.
- family
Solar thermal
An overview of solar thermal: hot water, combined solar heating and large installations. The SDHW is part of it.
See solar thermal → - vs solar
Heat-pump water heater
A heat pump on the air, not solar: hot water all year without collectors, ideal if the roof is not suitable.
Compare the heat-pump model → - to understand
Types of solar panels
Thermal for hot water, photovoltaic for electricity: understand the difference before choosing for your roof.
See the panel types → - to combine
Heat pump
As a backup to an SDHW or to heat the whole home, the heat pump is the ideal complement to a solar hot-water strategy.
Discover the heat pump → - budget
Solar water heater quote
Sizing, fitted price based on collectors and tank, and the share covered by Walloon or Brussels subsidies.
Request my quote → - ↑ category
All solar panels
An overview of solar with us in Belgium: thermal, photovoltaic, batteries and subsidies on one page.
Back to the solar guide →
Indicative price 2026
How much does a solar water heater cost?
The price depends on the type of collectors, the surface, the tank volume and the backup. Here are some benchmarks for an SDHW fitted in Belgium, subsidies deducted separately.
See the detailed SDHW price →* Indicative ranges for a fitted domestic SDHW, excluding specific configuration. Detailed estimate provided with your free quote.
- SDHW flat collectors from €4,5004 m² + 200 L tank, fitted
- SDHW evacuated tubes from €6,000better winter output, fitted
- Wallonia / Brussels subsidy up to €2,500depending on region and income
- Reduced VAT 6%in renovation (home > 10 years)
Solar water heater FAQ
Your questions about the SDHW
Does the solar water heater work in winter in Belgium? +
Partly. The collectors produce all year, but the low sunlight from November to February is not enough to cover all the needs. That is why a backup (electric element, boiler or heat pump) takes over in winter. Over the year, solar still covers 50 to 65% of your hot water.
Flat collectors or evacuated tubes? +
Flat collectors are robust, economical and suit most Belgian roofs. Evacuated tubes capture better in low sunlight and cold weather, so they improve the winter solar share, but cost more. The choice depends on your roof, your budget and your winter expectations.
What is the difference with a heat-pump water heater? +
A solar water heater uses thermal collectors to recover the sun’s heat. A heat-pump water heater is in fact a heat pump that draws heat from the ambient air, using electricity: it is not solar. The heat-pump model is self-sufficient all year and needs no roof collectors.
What collector surface and tank volume? +
For a household of four, you generally plan 4 to 6 m² of collectors and a 200 to 300 litre tank, about 50 litres per person. The sizing is matched to your real consumption to avoid both a hot-water shortage and summer overheating.
What maintenance does a solar water heater need? +
Maintenance stays light but necessary: you must periodically check the heat-transfer fluid (antifreeze water-glycol mix), the circuit pressure and the proper operation of the pump and regulator. A check every few years preserves the output and the longevity of the installation, which exceeds 20 years.
What subsidies for a solar water heater? +
Wallonia and Brussels support the SDHW with subsidies whose amount depends on your region and your income, and VAT drops to 6% for homes over ten years old. These aids significantly reduce the investment and the payback. We put together the subsidy file for you.
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