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Answer & Questions
Do you have any questions about your PV installation? In our FAQ we answer the most frequently asked questions from our customers simply and clearly.

Answer & Questions

Here you will find answers to some of the most frequently asked questions. If your question is not answered here, please feel free to contact us with your request. We endeavor to answer your request as quickly as possible.

Which roof pitch is ideal for photovoltaics? Basically, sloping roofs with a slope between 25 and 60 degrees are suitable for solar systems. The PV modules are installed on a flat roof using a mounting system, which enables the alignment and inclination to be ideally determined.

If you would like to estimate the maximum size of a photovoltaic system on your roof with a rough calculation, you can divide your usable roof area in square meters by ten. This gives you the maximum possible system output in kilowatts peak (kWp).

A special assembly device is used to fasten the photovoltaic modules, which is connected to the rafters via two rails. These rails usually run parallel on the underside. Alternatively, models with crossed rails are also available.

Outdoor photovoltaic systems along motorways or rail networks may only be built at a distance of at least 110 m. For systems in a commercial or industrial area, the areas used must already be designated as an industrial area.

The quick answer to the question: is my roof suitable for building a photovoltaic system? Basically, a roof with a slope of 30 degrees and an orientation to the south is ideal for solar power generation

The number of square meters for a photovoltaic system per 1 kW (kilowatt hour) fluctuates somewhat due to the different sizes of solar modules. As a “rule of thumb”, one can say that for 1kW approx. 6 / 6.5 square meters are required, with a 3.5 solar module and a 2.5 with the same size correspondingly more area.

150 kilowatt hours per square meter of solar surface in one year. A 30 m² photovoltaic system thus produces the annual electricity requirement (approx. 4,500 kWh) of a family of four. In order to achieve the highest possible self-consumption, the photovoltaic system should be around 40m² in size.

As a rule, the homeowner can install a solar system on the roof, which means that there is no obligation for third parties to install it. Manufacturers and suppliers, however, rightly recommend that the installation be carried out by skilled craftsmen.

When connected in series, the solar modules are interconnected one behind the other in what is known as a string and connected to the string inverter. The voltage of the individual photovoltaic modules adds up.

Solar modules in portrait orientation are modules that are mounted vertically or in portrait format on a roof. Alternatively, the modules can be arranged horizontally, i.e. H. be placed in landscape format or in landscape orientation.

According to the state building regulations, photovoltaic systems on roofs or on facades do not require approval in North Rhine-Westphalia. … Open-air photovoltaic systems are always subject to approval and require a building permit.

For so-called “building-independent” photovoltaic systems, however, the operators must comply with a building permit from a certain size. In almost all federal states, a height of 3 meters and a length of 9 meters are subject to approval.

If you want to build an island system, you are sure to ask yourself whether you need a permit for it. The good news first: in the vast majority of cases, no approval is required for an island system.

Depending on the rafter spacing, load and module size, around 2½-4 roof hooks are to be expected per PV module. Steeper roofs need more fastening elements, as do windy and snowy locations, the gable and the edges of the roof (since this is where the wind load is highest).

Basically, the installation and construction time depends on the size of the photovoltaic system. For PV systems up to 10 kWp the construction time is approx. 1 to 3 working days.

Often the size of the photovoltaic ground-mounted systems is given in hectares. In 2018, the nominal output of an average ground-mounted system was 0.9 megawatts peak per hectare, older systems have lower values.

A yield of 950 – 1,000 kWh per year is assumed for a kWp. Therefore, a yield of approx. 135 kWh to 140 kWh can be assumed for one square meter.

Calculate 800 kWh to 1000 kWh per kilowatt peak (kWp) of installed photovoltaic capacity.

A solar system with 5 kWp output is usually sufficient to cover the entire electricity requirement for a single-family home.

In a normal single-family home, a photovoltaic system pays for itself for around € 8,400 after around 10 to 12 years. It is even faster if you invest up to € 12,000 at the beginning. Due to the high electricity price, there is a good balance to the low feed-in tariff for profitability.

Photovoltaic systems are connected to the public power grid by the licensed electrician and registered with the local grid operator responsible for the feed-in.

Installation of photovoltaic systems. Only qualified electricians can connect photovoltaics correctly. Because numerous cables have to be laid from the roof into the house.

As a rule, the installation of a solar system is carried out by the specialist company who has already planned the system – or by a craftsman commissioned by the company.

Individual solar cells usually generate an electrical voltage of 0.5 V – 0.6 V. To build up a higher voltage, they are connected in series in the solar module. With power sources connected in parallel, the current strength increases (measured in amperes). The electrical voltage in volts remains the same.

The interconnection of a module field has a serious influence on the electrical properties. If several modules are connected in series, the voltage of the entire string increases. If the module has a voltage of 30V, a string voltage of 300V results for a string with 10 modules.

Photovoltaic modules convert the light from the sun directly into electrical energy. The sunlight causes an electrical voltage in the solar cell, which is picked up on the surface. Several solar cells are electrically interconnected in a photovoltaic module.

In the case of on-roof installation, the solar modules are mounted on a metal frame over the roof tiles. Roof hooks are used to fix this metal frame on the roof. These are U-shaped and are screwed onto the rafter under the roof tile and led to the outside at the lower edge of the roof tile.

  • Photovoltaic solar modules.
  • Solar cable.
  • If necessary a solar battery (battery)
  • an inverter that converts the direct current generated by the system into usable alternating current.

Mini-PV systems as balcony power plants. The installation of so-called balcony power plants has been permitted in Germany since 2018.

What does “building-independent” mean? According to our research, the phrase “building-independent” is intended to describe the installation of solar systems on open spaces, i.e. not solar systems in or on roof and exterior wall surfaces.

A photovoltaic system is worthwhile because it pays for itself after around 10 to 15 years. With a service life of 25 years or more, this means that you will only generate profits over 10 years and save a decisive part of your electricity costs.


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Our international partners

We are very grateful for the support of our international partners, with whom we have grown together and have been able to build up a great network over time. Many fruitful collaborations have emerged from this so far and will arise several times in the future.

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