Size Requirements

Hot water production installations are sized according to the number of people in the household. Surfaces of 1.5 m² per person of flat collector, or 1 m ² per person of vacuum tube collector can be considered to be indicative requirements. The tank should have a capacity about 80 litres per person. It is recommended that you contact specialist contractors who will perform more precise calculations for heating support facilities.  The advice of a professional, the correct installation setting and control of the operation with the aid of a heat meter by the fitter are essential at any rate.

Economy and life of the installation

Installations with flat collector panels have an annual output from approximately 400-500 kilowatt hours per square meter of the collector’s surface, which corresponds to approximately 40 to 50 liters of fuel oil or to 40 to 50 cubic meters of natural gas. Quality installations produce in two to three years the energy which was necessary for their manufacture. The installation has a lifespan of 25 to 30 years.

Costs and profitability

The cost of a solar water heating installation with flat collector panels varies from 1,000 to 1,200 euros (about $1,400 to $1700) per square meter of collector surface. This includes the costs of the solar tank, piping and the regulation system. Financial depreciation is largely dependent on the prices of energy. By including State and municipal aid as well as an energy price inflation rate of 4% per year (currently higher), a solar water heating system pays for itself in approximately 25 years.

Slope of the roof and orientation

If you are located in the Northern hemisphere, the collectors must be directed, in principle, towards the south. A variation of 45° compared to the correct orientation to the south causes a loss of output which can reach 10%. The optimal incline of the collectors in relation to the horizontal plane in European areas around Luxembourg, for example, is between 30° and 50°.

An alternative way

The combination of a solar installation with a boiler which uses granulated wood (ie pellets) is optimal from an environmental point of view. The use of renewable raw materials (wood) and solar energy generates practically no Carbon Dioxide emissions. The combination with a condensing boiler also constitutes an interesting and economic alternative.

Based on a report from The Town of Luxembourg.
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