A solar module is an array of small interconnected solar cells. The front of the module is covered by toughened glass, while at the back, protection is usually provided by a plastic film.

Each one of these solar cells is made up of razor-thin layers of semiconductor material. Between their contact faces a potential difference is created by the influx of sunlight.

The solar energy produced is converted by an inverter into AC, matching the mains supply and connected directly to the mains via a second electricity meter. Thus the PV system is technically independent of the domestic mains and electricity is charged or credited separately. 

N.B. The efficiency of a solar installation in Germany is optimized if the modules face south and if they are installed at an angle between 25 and 40 degrees. However, there is scope for alternatives.

 Note:

Shadows cast onto the modules (e.g. by trees) can considerably lower the yield.