Frequently asked questions

In solar thermal energy, collectors convert solar radiation into usable heat. It is usually used via heat exchangers for heating and hot water preparation.
Photovoltaics is the direct conversion of solar energy into electricity using solar cells, which are installed in large panels known as solar modules.

A solar cell is a thin, approximately 15 x 15 disc, usually made of silicon and/or another material.

Contact strips are attached to the front and back of the disc, which conduct the electricity generated by the sunlight into the cell. The silicon is made from quartz sand.

These cells are assembled into large plates, the panels.

The installation time is divided into the quotation and preparation phase and the actual construction phase.

All in all, please allow at least 2-3 weeks. In individual cases, it can also take 8-12 weeks due to delivery delays.

The actual construction phase of a photovoltaic system depends on the output size and the structural conditions. For systems up to 10 kWp, installation usually takes one to three working days.

PV systems can be installed on flat roofs without any problems.
On flat roofs, the modules are installed at an angle using a mounting system so that they have an optimum south-facing orientation and a favourable inclination. At the same time, the inclined position of the modules ensures that no deposits from rain or dust form on them and that there is sufficient ventilation.
A sufficiently large distance between the modules is important here, too, as otherwise there will be shading and thus a reduction in yield.

To install the same output, the required flat roof area is approximately twice as large as for a pitched roof variant.

The amount of solar power generated depends on the location, the inclination and orientation, and the solar modules used.

In Germany, a photovoltaic system generates an average of around 1,000 kilowatt hours of electricity per kWp, whereby the electricity yield in southern Germany is often slightly higher than in northern Germany.

Photovoltaic modules not only utilise direct sunlight when the sky is clear, but also the diffuse radiation that passes through clouds or fog.
The brighter th elight is, the more power the modules produce - regardless of whether the sun is directly visible or not. 

In Germany, the diffuse radiation accounts for around half of the overall irradiation.

Rarely, because the smooth module surface means that rain and snow normally take care of the cleaning.

However, cleaning is recommended every five years or so, or more frequently in areas with heavy soiling.

Some dirt or bird droppings are not simply washed away by rainfall and reduce the performance of the system in the long term.

Before the installer is commissioned, the grid connection must be clarified, as the grid operator may have additional requirements, especially for larger systems.
As a rule, no special authorisations need to be obtained for private systems on detached houses or apartment blocks. You still have to submit the so-called "grid feed-in enquiry" (Einspeiseanfrage) to your regional grid operator.

But don't worry: we'll take care of it for you!

Depending on the age of the house, you may need to take into account any listed building requirements.
Very rarely, planning permission is also required. You should therefore enquire with the local authority or municipal office at an early stage.

Once the system has been completed, the location and output must be registered with the Federal Network Agency.
If you forget to register, you could be fined.

We will also take care of this registration for you!

For a family of four, you can expect a total of 3,500 to 4,500 kWh of electricity consumption per year if no electricity is used for heating or hot water.

Depending on the cell type, 30 - 40 m² of module surface area is required to generate this amount of electricity. This corresponds to a system output of around 5 kWp. If the roof area allows for a higher output, this can of course also be utilised depending on the customer's requirements.
With a battery as storage, the energy generated can be better utilised for self-consumption, especially at night. Then, if possible, a system with 10 kWp or more also makes sense.

Oversized systems without a battery are generally not worthwhile because the feed-in tariff is very low.

There are a number of funding opportunities, but the nationwide funding programme has now been fundamentally revised several times, even at short notice.
It is therefore worth enquiring about the current status from the funding organisations, the KfW bank and the Federal Office of Economics and Export Control (BAFA).

In addition, there is regional funding in some municipalities. Here, too, it makes sense to enquire at the citizens' office or local authority.

Yes, investing in a PV system is still worthwhile, but now mainly for your own electricity consumption.

Self-generated electricity is considerably cheaper than electricity purchased from the public grid. Together with a battery storage system, you can beat the ever-increasing cost of electricity.
The more of your electricity requirements you cover with self-generated electricity, the less you have to buy from external electricity suppliers.

And for the electricity you don't use yourself and feed into the public grid, you also receive a state-guaranteed feed-in tariff for 20 years.

Yes, an east-west orientation can sometimes make more sense, indeed, as most of the electricity generated is consumed when someone is at home. The sun is in the east in the morning and in the west in the evening, which makes an east-west orientation particularly attractive for working people.

Yes, income from the operation of a photovoltaic system must be recognised for tax purposes and reported to the relevant tax office. Detailed information on the tax assessment of photovoltaic systems can be found here.

The answer, as almost everywhere, is: It depends.

The same rule applies to PV systems: buy cheap, buy twice.
With PV systems, it is not just the components, such as panels, inverters and batteries, that are either durable or not. The most important factor is the quality of the installation work.
And craftsmen who work properly are more expensive than those who work poorly.
All of this is reflected in the price of the system.

Poorly laid cables, broken roof tiles, and even properly processed plug connections can quickly lead to subsequent and expensive repairs, which can turn what should be an inexpensive system into an expensive pleasure.

As an estimate, the price range for a PV system is about 2000 - 3000 Euro per kWp.