Solar panels have become even more efficient

Solar thermal: use solar energy for heating and hot water

If you want to know whether your property is suitable for a solar system, you can get advice from an energy advisor at home. The solar suitability check is available for 30 euros. Register your request for advice on: 0800–809 802 400.

This is how much you can save with solar energy

When heating water

To meet the annual hot water requirement of 4 people, you need around 4,200 kilowatt hours of energy. A solar system can take over 50–60 percent of this. With an energy price of 6.7 cents per kilowatt hour (ct / kWh) of natural gas, the system saves around 140 euros per year. If the energy price rises by an estimated 3 percent annually, these savings add up to 3,800 euros over 20 years.

The solar system avoids around 450 kilos a year CO2 emissions. Over an assumed service life of 20 years, that is 9 tons less CO2.

With heating support

The energy requirement for heating and hot water in a building with 150 square meters of living space is, for example, around 15,000 kilowatt hours per year [kWh / a]. A solar system can take over 25 percent of this. At an energy price of 6.7 cents per kilowatt hour (gas), the system saves around 250 euros per year. If the energy price rises by an estimated 3 percent annually, these savings add up to around 6,500 euros over 20 years.

The CO2 emissions can be reduced by around 750 kilos a year. Extrapolated over 20 years, that's 15 tons less.

Requirements for an optimal yield

So that you can use your solar thermal system as optimally as possible, the following factors are decisive:

Size of the collector area -for water heating

As a rule, for a 4-person household you need a collector area of ​​5–6 m2 (flat plate collectors) and buffer storage with a volume of 300–400 liters to cover 50–60 percent of the annual energy requirement for hot water preparation via the solar thermal system cover. If you also want to supply a washing machine and / or dishwasher with hot water, you have to add 30–50 liters per device.

This design is based on the assumption that your hot water needs make up around 25-30 percent of your total water consumption.

Size of the collector area - for heating support

Here you will often find systems with at least 10–15 m2 collector surface (flat plate collectors) and a buffer tank between 700 and 1,200 liters. With a solar thermal system of this size, you can roughly cover 10–20 percent of the heating energy in an old building and 25–40 percent of the heating energy in an energy-saving house (solar coverage).

Orientation and inclination of the collectors

The sun shines relatively steeply on the roof in the summer months. Therefore, the slope of the collectors can be flat to provide warm water. For a solar system with heating support, however, a roof pitch of 45–55 degrees and an orientation to the south (up to a deviation of 15 degrees) offer very good conditions. In this way, the collectors can also catch the sunlight falling at an angle in autumn and spring and use the heat generated to cover a large proportion of the power required for heating. With a less sloping roof, you can still achieve the desired yield with a slightly larger collector area.

Try to avoid shadows on the collectors - for example from chimneys, dormers, satellite receivers, neighboring buildings and trees.

What to do if the solar system does not run optimally?

Don't you have enough hot water in the summer months? The system is making noises? Is it getting too hot? Are water and steam flowing out? Then your system is obviously not running optimally. Long-term problems can usually be traced back to errors in planning or assembly as well as a lack of maintenance.

Air in the solar circuit or a missing blow-off line can also cause disruptions in the operational process.

Where the fault is and how it can be rectified can usually only be clarified on site by specialists. It is therefore best to request the help of a solar specialist company or installer.

Further information on costs and benefits, possible uses and requirements of a solar thermal system can be found in our "Heating" guide and in the "Electricity and heat: ways to energy self-sufficient house" guide.