Information on topics related to solar energy and its possible uses

All legal statements in these FAQs refer to German law. If you have any questions about the legal situation or other important information in other countries, we will be happy to help.

The legal situation and other regulations at Solar are in flux due to rapid further developments. These FAQs do not cover everything there is to know about Solar and there may always be changes that are not yet reflected on this homepage.

The new Renewable Energy Sources Act contains clear simplifications and improvements in terms of consumption, but also the generation of self-generated electricity.
The feed-in is now remunerated at a higher rate.
If installation on the roof of the house is not possible, a system can be set up in the garden as an alternative. There is now funding for this as well.

Photovoltaics takes sunlight and converts it into electricity, more specifically direct current. The photovoltaic system consists of solar modules containing solar cells that absorb sunlight. The direct current generated is then converted into alternating current at 230 volts, known as household electricity, via the enclosed inverter.

In solar thermal energy, light is converted into heat.
A solar thermal system harnesses solar energy for domestic water heating and heating support. Unlike photovoltaics, no electricity is generated, but heat is. The main benefit of solar thermal in terms of efficiency is in the autumn and winter months.

Many cities, districts and states have set up funding programs.
You get a fixed feed-in tariff from the state for the first 20 years for the solar power fed into the grid.
The KfW grants low-interest loans for systems and also electricity storage.
We refer to the local conditions and any changes in the funding landscape. Things are moving in a very good direction.

High degree of independence from the public power grid. You can also earn money with it. In addition, you also increase the value of the house.

As a renewable energy source, solar energy plays an important role in reducing greenhouse gas emissions and mitigating climate change. This is vital to protecting people, animals and ecosystems. Solar energy can also improve air quality and even reduce water consumption in energy production.

In addition to sunlight, solar modules also use the brightness when it is overcast outside. The brighter, the more electricity.

The inverter or the battery storage can determine when excess solar power flowing into the grid is being produced. With many devices, you can control a special consumer to use this solar power yourself.
A heat pump is suitable for this if a heat accumulator is available. This can be a larger water reservoir, or reservoirs in floors and walls. This works perfectly when the power consumption of the heat pump can be adjusted to the available solar power.

The roof surface should not be in the shade, or as little as possible. The roof should be sufficiently stable for this. A southern orientation of the roof is ideal. The ideal angle of inclination of the roof is 30 degrees. Inclines between 25 and 60 degrees are almost as good. Outside of this range, you can still count on about 90% of the optimal performance of a 30-degree roof.
The orientation of the house roof and the solar radiation are therefore relevant in relation to the performance of the system.

East and west orientations also make sense, even if they deliver a little less power. In the morning and in the evening, the system performs better here. So the power generation is a little less, but it is stretched over time.

Especially with new buildings or roof renovations, the modules can be integrated directly into the roof construction instead of assembly
up over the roof. The orientation of the house roof and the solar radiation are therefore relevant in relation to the performance of the system.

East and west orientations also make sense, even if they deliver a little less power. In the morning and in the evening, the system performs better here. So the power generation is a little less, but it is stretched over time.

It is important that light, i.e. brightness, is available. Plants facing south bring the greatest yield. If the system is oriented towards the south-west or south-east, the yield is only slightly reduced.
The optimum angle of inclination is around 30°. Even if this cannot be adhered to, the restriction in the range from 0 to 50° inclination is small. Shady areas, e.g. caused by other houses or trees, are worse.

The service life is on average more than 40 years. Performance guarantee is usually granted for 25 years, which means that the solar module must still generate at least 80% of the originally specified performance within this period.
The module manufacturers give a performance guarantee of 25 years. Optical changes do not result in a warranty claim.

An inverter converts the DC voltage coming from the system into AC voltage. It also synchronizes the frequency with the public power grid. In the event of faults, the monitoring device disconnects the system from the network.

Net metering allows your utility to measure the direction of electricity flow to and from your home.
If you generate more electricity than you use, you can use this system to send the energy you don’t need back to the grid in exchange for a credit note (from 2024).
So you only pay for the difference between the energy generated by your system and the total energy you use.
That means exactly that the energy generated by your solar system is remunerated by your energy supplier.
This reduces your risk in the event of electricity price fluctuations. The higher the electricity prices rise, the more valuable it becomes.

kWp is the abbreviation for kilowatt peak. The value indicates the peak output (= nominal output) of a photovoltaic module under standard test conditions with an ambient temperature of 25°C and an insolation of 1000 W/sqm.

A kWh is the unit of measurement for electricity generated under real conditions. One kilowatt hour corresponds to the energy that can be generated by a 1 kW system per hour.

If the grid fails or is switched off, the photovoltaic system also switches off automatically and immediately. To do this, the inverter of the photovoltaic system constantly monitors the state of the power grid based on voltage and frequency.
It must be switched off in the event of faults, otherwise electricity would be fed into the grid and this would pose a risk to electrical systems in the grid and to the electricity staff working on the grid.
When the photovoltaic system is switched off, no electricity comes from the battery storage system either, unless it has an emergency power function and supplies the circuits in the house isolated from the mains.

In our latitudes, precipitation is usually sufficient for cleaning.

If you still want to clean the system manually, be sure to use lime-free, dematerialized water. Great care is required here in order not to scratch the solar modules. Never use a high-pressure cleaner. It is always better to hire a professional.

Solar power can also be produced in winter. Roughly speaking, this amounts to about a third of the total annual production. However, snow-covered solar modules have little to do with it. The enemy of snow is the sun, even in winter. And it can slide down too.

Snow-covered collectors reduce electricity production at low and medium altitudes by between one and eight percent.

The solar system can also be operated in winter when there is snow without any further measures.

In these cases, there is relatively cheap insurance. You are not obliged to take out insurance. However, should you do this, which we also advise you to do, you must report the conclusion of the separate insurance for photovoltaics to the insurance company with which you took out your household contents insurance. If you see an additional risk potential for your property in the PV system, you can contractually adjust the residential building policy. Under no circumstances should you fail to inform your insurer about your PV insurance, otherwise they may refuse to pay in the event of damage to your building.

For protection there are lightning protection and fire brigade switches. However, there is no government obligation to install a lightning protection system.
When taking out photovoltaic insurance, however, most insurers require proof of the installed lightning protection.
Lightning protection is generally recommended for systems from 10 kWp.

Walking on the modules is discouraged thought solar modules are very robust, especially against weather phenomena to a certain extent.

Nevertheless, people should not sit, lie, stand or walk on modules. Heavy loads can become dangerous, from visible to invisible damage such as small cracks.

If the module surface still has to be walked on, it is better to use suitable step pads or, ideally, to hire a specialist to do it.

There is an association called “PV-Cycle” for this purpose. Part of the recycling fee is included in the purchase price of a new module.