The basic unit of a photovoltaic system is a solar module in which numerous solar cells are interconnected electrically. Several modules are combined in a solar generator. The direct current generated by the solar cells is fed to the inverter via d.c. circuits. This device converts the direct current into alternating current which is fed into the public mains via a meter in case of a grid-connected photovoltaic system. In times lacking sunshine, the current is received from the mains - the public mains serve as a storage tank for the photovoltaic system.

In all regions of Germany, the intensity of radiation is high enough to operate photovoltaic systems. In general, photovoltaic systems can be installed wherever enough  incident light radiation is given. Optimum yield is achieved by a pane with an inclination of 30° oriented to the south. A deviation to southwest/southeast or inclinations between 25° and 60° reduce the yield only slightly. Shadowing by trees, houses next door, gables, antennas, etc. should be avoided as they reduce the current yield considerably.

Due to the favorable conditions of remuneration, it is recommended to design the solar system not only according to your own current consumption but according to the size of the suitable roof pane and your budget. A photovoltaic system with a rating of 1,000 watts (1 kWp) requires a roof pane of about 8 to 9 m².

As a general rule in this part of the world, an energy yield of at least 800 kWh per kWp of installed capacity of the system and year can be achieved. Accordingly, a photovoltaic system of 2 kWp with a size of about 20 m² already generates about 1,600 kWh solar power per year.

No, the current can also be consumed by your own household and only the excessive power is fed into the mains. However, only the complete feeding (EEG) is profitable under economic aspects due to the higher remuneration. Moreover, solar power can be used wherever no mains connection is available, e.g. for solar garden lamps, solar pumps for garden ponds, or small electronic devices. In order to increase supply guaranty, these so-called "island systems" are often provided with an accumulator as energy storage.

Photovoltaic modules can be installed on almost all types of roofs. If they are installed in a clever way, they are an eye-catcher - the building is upgraded. The modules can be installed in four different ways. On-roof, in-roof installation, free installation, and façade installation. When selecting the type of installation, visual and architectural aspects play an important role in addition to the most favorable orientation and inclination of the modules.

In almost all German Länder, a building permit is not required for a solar system on a single family house which is normally installed on the roof or integrated in the roof. The duties to obtain a permit are subject to the building regulations (LBO) of the Länder. They can be browsed under www.bauordnungen.de. Limits beyond which a permit is required are mentioned in the regional building regulations. Often the size of the systems which do not require a permit and/or buildings, carports, etc., on which the solar systems are to be installed are affected. This also includes all systems which are not installed on roofs such as field installations and façade systems and/or overhead systems. We recommend to read the regional building regulations before installing a system and/or to ask the building authorities for duties to give notice or to obtain a permit.

The manufacturers of solar modules offer warranties ranging from 10 to 25 years. The average service life of photovoltaic modules amounts to 30 to 40 years. In general, a photovoltaic system is almost maintenance- and trouble-free.

Solar power systems are almost maintenance-free. This is why the operating and maintenance costs for photovoltaic systems are very low. The most important task is regular reading of the current meter in order to detect a failure early although failures rarely occur in practice. Dust and impurities on solar modules are usually removed sufficiently by snow and rain. Major impurities (such as leaves and bird droppings) which cause real partial shadowing of the system are to be removed as soon as possible.