« Devis clair, sans surprise, primes comprises. Un seul interlocuteur du début à la fin. Je recommande sans hésiter pour le photovoltaïque. »
Pierre M.Tournai
Solar energy · Thermal
Solar thermal: the sun’s heat, not its electricity
Where photovoltaics produce power, solar thermal captures the sun’s heat directly to warm your water and support your heating. With a much higher yield per square metre, a few collectors are enough to cover a large share of your hot-water needs — and to ease the load on your boiler or heat pump.
- 4–6 m²
- of collectors for a family
- 60–70%
- of annual DHW coverage
- 20 years +
- lifespan
Up to 80%of hot-water needs
High yieldper m² of roof
How it works
What solar thermal really does
The principle is simple: a fluid heated by the sun in the collectors releases its heat into a storage tank. Here are the benchmarks that matter before you commit.
- Principle Direct heat
A dark collector absorbs the radiation and heats a heat-transfer fluid. That fluid flows to a tank where it warms the water via an exchanger. No conversion to electricity: the heat is used as is, hence the excellent yield.
- Yield per area 3 to 4× vs PV
Per square metre, thermal converts far more solar energy into usable energy than photovoltaics. To produce hot water, 4 to 6 m² of collectors are enough where you’d need a much larger PV panel area.
- Hot water (SDHW) 60–70%
The individual solar water heater covers 60 to 70% of a Belgian household’s annual hot-water needs, and up to 80% in summer. The rest is handled by the backup (boiler, heating element or heat pump).
- Heating support (CSS) +15–25%
The combined solar system adds heating support: it pre-heats the heating circuit in the mid-seasons and can cut annual consumption by 15 to 25%, especially with low-temperature heating.
- Collector types Flat / tubes
Flat-plate collectors, robust and economical, suit hot water. Evacuated tubes, more effective in cold weather and low sunlight, are preferred for heating support and less favourable climates.
- Annual coverage Seasonal
In Belgium, production is strong from April to September and lower in winter. Hence the importance of a well-sized tank and an efficient backup to ensure comfort all year round.
* Indicative values for a properly sized and oriented domestic installation. Actual coverage depends on exposure, tilt and your consumption — clarified at the survey stage.
In full transparency
Solar thermal: benefits & limits
Thermal is unbeatable for hot water, but it’s not a universal solution. Here, honestly, are its strengths and the points to watch.
Where it shines
- Highest yield per m²A few collectors cover a large share of hot-water needs.
- Lighter hot-water billUp to 70% of DHW needs covered, so much gas or electricity saved.
- Ideal as a complementPairs with a boiler, a heat pump or a heating element for year-round comfort.
- Clean, lasting energyCollectors reliable for 20 years and more, with no emissions in use.
What to keep in mind
- Seasonal productionLower in winter in Belgium: a backup remains essential all year round.
- Produces no electricityTo power your appliances you need photovoltaics, not thermal.
- Storage to size carefullyA tank that’s too small wastes the summer surplus; the calculation is essential.
- Summer overheating to manageIn summer the collectors can overproduce: suitable regulation and dissipation are needed.
For which project
Is solar thermal right for you?
It comes into its own wherever there are regular hot-water needs and a well-exposed roof. A few cases where it makes the difference:
-
Plenty of hot water
Large family, daily showers, a bathtub: the more hot water you use, the more profitable a solar water heater is. The thermal use case par excellence.
-
Heating support
With low-temperature heating (underfloor or oversized radiators), a combined solar system eases the boiler in mid-season and cuts the heating bill.
-
Pool heating
To extend the swimming season, dedicated collectors warm the pool water at little cost, with no gas or backup electricity.
Electricity instead, or hot water only?
If your priority is producing your own power, look instead at photovoltaics. And if you only want domestic hot water, the solar water heater is the most direct solution.
Glissez la poignée pour comparer
Real case · family home, Namur
Four people, 70% of the hot water provided by the sun
A family of four heated their water with gas all year round. We installed 5 m² of south-facing flat-plate collectors and a 300-litre solar tank, wired to pre-heat the existing boiler. The result: most of the hot water now comes from the sun, and the boiler only takes over as backup.
- 70%of hot water from solar
- 5 m²of flat-plate collectors
- 300 Lsolar tank
Customer reviews
They chose wendows
5.0/5 · 1verified reviews
Compare the options
Solar thermal, or another solution?
Thermal excels at heat, photovoltaics at electricity. Compare them point by point, then open the application that fits your project.
| Critère | Solar thermalVous êtes ici | Solar water heaterVoir la gamme → | PhotovoltaicsVoir la gamme → |
|---|---|---|---|
| What is produced | Heat (water + heating) | Heat (hot water) | Electricity |
| Yield per m² | The highest | Very high | Lower |
| Main use | Hot water + support | Hot water only | All appliances |
| Winter production | Reduced | Reduced | Reduced but useful |
| Area needed | 4–6 m² | 3–5 m² | Larger |
| Needs covered | DHW + part of heating | DHW only | Household electricity |
| Ideal for | Hot water + heating | Everyday hot water | Electrical independence |
Indicative benchmarks for common domestic installations. Thermal and photovoltaics are complementary — we define the right mix together at the survey stage.
- application
Solar water heater
Domestic hot water from the sun: the SDHW covers 60 to 70% of a household’s needs. The most widespread thermal solution.
Discover the water heater → - application
Pool heating
Dedicated collectors warm the pool water to extend the swimming season, with no gas or backup electricity.
Heat my pool → - vs thermal
Photovoltaic panels
To produce your own electricity rather than heat. Often complementary to thermal on the same roof.
Compare PV → - to combine
Heat pump
A heat pump can serve as an efficient backup to solar thermal for heating and hot water the rest of the year.
See heat pumps → - alternative
Thermodynamic water heater
An alternative to solar hot water: it draws heat from the ambient air to warm the tank, in any season.
Discover the thermodynamic one → - ↑ category
All things solar
An overview of solar energy in Belgium: photovoltaics, thermal, storage, grants and installation on one page.
Back to the solar guide →
Indicative price 2026
How much does a solar thermal installation cost?
The price depends on the application (hot water only or heating support), the type of collectors and the tank size. Here are benchmarks for equipment installed in Belgium.
Request an itemised estimate →* Indicative ranges for an installed domestic system, excluding specific configurations. Itemised estimate at your free quote.
- Solar water heater (SDHW) from €4,500flat-plate collectors + tank, installed
- Combined solar system from €9,000hot water + heating support
- Energy grant up to €1,500depending on region and performance
- Reduced VAT 6%in renovation (home > 10 years)
Solar thermal FAQ
Your questions about solar thermal
What’s the difference between solar thermal and photovoltaics? +
Solar thermal captures the sun’s heat to warm water or support heating, while photovoltaics convert light into electricity. Thermal has a far better yield per square metre but produces no power: the two are complementary and can coexist on the same roof.
Does solar thermal work in Belgium? +
Yes, very well. Belgian sunshine is enough to cover 60 to 70% of a household’s annual hot-water needs, and more in summer. Production is lower in winter, which is why a backup (boiler, heat pump or heating element) always complements the system.
Flat-plate or evacuated-tube collectors? +
Flat-plate collectors are robust and economical, perfect for domestic hot water. Evacuated tubes offer better yield in cold weather and low light: they’re preferred for heating support or less well-exposed roofs. The choice is made according to your project and your roof.
Can solar thermal heat my house? +
Partly, via a combined solar system (CSS). It pre-heats the heating circuit in the mid-seasons and cuts annual consumption by 15 to 25%, especially with low-temperature heating. It doesn’t replace your boiler or heat pump, it eases the load on it.
What grants are there for solar thermal in Belgium? +
Depending on your region and income, an energy grant can reach €1,500 for a solar water heater or combined system, on top of the 6% VAT for homes over ten years old. We handle the grant application for you.
Do I have to choose between thermal and photovoltaics? +
Not necessarily. If your priority is hot water, thermal is the most efficient per square metre. If you want electricity, it’s photovoltaics. Many households combine both: we define together the most profitable mix according to your roof and consumption.
Get your free solar thermal quote within 48h
Roof survey, tank sizing, grants calculated, a single point of contact. Describe your project in under a minute.
- Free and no obligation
- Grants & 6% VAT handled for you
- Installed by our certified fitters