A solar water heater is a device that captures sunlight to heat water. It can be an economical way to generate hot water for your family (for shower and bath).
A solar heater not only enables substantial energy savings as solar power is free in contrast to natural gas or fuel oil. Moreover, it is a way to produce hot water for sanitary use throughout the year without emitting any CO2.
In our latitudes, the sun shining on 1m² of roof replaces 100 l of heating oil or 100 m³ of natural gas (approximately 1 000 kWh) a year. Generally speaking, it is possible to heat 50 to 70 % of the water used in the kitchen and the bathroom in this way. However, a back-up heating system is required for times when there is insufficient luminosity.
Supplying a washing machine or dishwasher with this hot water also cuts out the electricity used by these appliances to heat the water and shortens the washing cycles, as long as certain precautionary measures are taken.
The efficiency of the collectors is at its highest at midday, in summer, when the sky is cloudless, and when the collectors face south.
However, the collectors also work well in other seasons, when the sky is cloudy, for a good part of the day, even if they face east or west.
Likewise, the efficiency is best at a gradient of 35° to the horizon, but good results can be achieved with collectors fitted vertically to a façade.
A basic solar water heater (i.e. for a family of 4 people, demanding 200 to 300 litres, with 3 to 5 m2 of solar collectors) costs on average € 4,500 to € 6,000, including VAT and installation. To help you with this investment, the Brussels Region gives you an energy grant, which is supplemented by certain communes.
Wondering whether your roof suitable for a solar water heater?
Depending on the region of residence, you will find different solar mapping tools on the suitability of your roof.
The solar water heater absorbs light by means of a collector placed on the roof and converts it into heat.
The heat is then passed to a water tank by means of a circulating pump. This exchange is triggered by the thermal regulator, but exclusively when the collector is hotter than the water in the tank. This not only prevents the circulating pumps from needlessly using electricity but conversely, also avoids overheating.
When there is insufficient sunlight, the water is preheated and a back-up system takes over to bring the water to the required temperature. This system can therefore be used at a constant temperature throughout the year.
Subscribe to our newsletter and stay informed about energyfacts.