Solar systems – generating electricity and heat from solar energy

It is doubtful whether the discoverer of the photoelectric effect, the French physicist Alexandre Edmond Becquerel, had already guessed in 1839 that the solar requirement for certain areas would come into force by law in some German states in 2022. But he took the first step towards PV technology. However, the first “flat plate collector with a glass cover”, which was able to reach a temperature of more than 80 degrees Celsius, was built by the Swiss botanist and natural scientist Horace Bénédict de Saussure. After numerous further developments, the American metal manufacturer Clarence M. Kemp was able to patent his functioning solar system in the form of a storage collector in 1891, in which water was heated by the power of the sun.

Today, solar thermal energy and thus solar systems play a crucial role in the expansion of renewable energies. This also includes small photovoltaic systems that can be installed on balconies. What balcony power plants are, how they work, whether there are requirements or restrictions or whether energy can be stored, this can be found in the following notes. Here you can also find out what should be taken into account when choosing a location, how the electricity generated is fed into the grid and how the electricity generated is remunerated. Of course, the advantages of balcony power plants, their amortization and the question of what should be taken into account when buying a balcony solar system are also discussed.

Balcony power plants – what does that mean?

Balcony power plants are photovoltaic systems (PV systems), so-called plug-in solar devices, which are also known under the name mini-PV, balcony solar system, plug-in photovoltaic system, socket solar device, balcony module, guerrilla PV or plug-in system. The balcony power plants are installed on balconies or other open areas (e.g. roofs, carports, walls, etc.) and generate free electricity from solar energy in an environmentally friendly and resource-saving manner. It is therefore possible to partially cover a household's electricity needs with a balcony power plant. This means a permanent reduction in electricity costs. 

Photovoltaic systems are ideal when it comes to sustainable savings in electricity costs and independence from the public power grid, especially in view of rising electricity prices. If the balcony power plant is combined with an infrared heater, not only electricity but also heating costs can be reduced. The fact that the need for fossil fuels is minimized is not only positive for costs, but also for reducing economic and political dependencies.

Structure and functionality

Balcony power plants usually consist of one, two or even four standard PV modules with an output of 300, 600, 800 or 1500 watts. In order to be able to convert the direct current generated into alternating current, a small inverter is attached to the back. A cable leads from this inverter and must be connected to a power cable. The plug located at the other end of the power cable must now be connected to a 230 volt socket on the balcony or in the apartment.

Once this has happened, the balcony power plant is connected to the house network. When sunlight hits the PV module, electricity is generated and fed into the home network to supply the devices in need, such as the refrigerator. As a result, less electricity is consumed from the network, the electricity meter runs slower and electricity costs are saved. Excess electricity that is not needed is automatically released into the public power grid.

The installation of a plug-in solar system up to 600 watts can also be carried out by ordinary persons. However, if the small power plant has over 600 watts, then it is necessary to call in a specialist (electrician). After the installation or commissioning of a balcony power plant, the network operator must be informed. Plug-in solar systems with an output of up to 800 watts must be registered and deregistered with the Federal Network Agency.

Location, requirements and limitations

If you are a tenant who would like to install and use a balcony power plant on your balcony or terrace, it is advisable to speak to your landlord or the homeowners' association in advance and obtain permission in this regard. This should be set out in writing or noted in the rental agreement. This is the only way to prove that the tenant has permission to operate a solar system, even if the landlord changes.

This landlord's permission is required because, on the one hand, attaching the balcony power plant to the outside of the balcony changes the appearance of the building and, on the other hand, a structural change is made to the building when it is attached to a wall. It should not be forgotten that feeding electricity into the building network can also be viewed as a change and requires landlord permission.

Although a small solar system is mainly found on balconies, it is also suitable for installation on balcony railings, on the terrace, on the house facade, on the gazebo and on a sloping roof. A balcony power plant can even be found on a garden table. However, there are a few criteria to consider:

• The Balcony power plant must be installed in a place where the PV module receives the longest amount of sunlight during the day. In the direction of the compass there is no need to pay attention to high efficiency in energy production. To ensure this, the solar system should be aligned with an inclination angle of 30 to 35 degrees to the south. The balcony power plant should be mounted on a frame with angular inclination, which is usually included in every complete package.
• It is also important that the small photovoltaic system - which feeds the green electricity generated from solar energy into the house network - is installed where there is an appropriate power source in form of a socket.
• The PV system must be installed in such a way that it cannot crash. It should be considered that an angle of inclination of ten degrees is already considered a canopy and for safety reasons (glass shatters and can lead to injuries), no one should stay under it.
• However, vertical installation is possible and is not a legal problem. An alternative would be plastic modules. These can be attached with an angle of inclination of ten degrees,
• If the balcony power plant is to be installed on a flat surface such as a terrace or flat roof, it must be weighed down to avoid damage from gusts of wind.

Storage, feed-in and compensation

The electricity generated from solar energy using a balcony power plant is mostly consumed by the owners themselves. However, if more energy is generated than is consumed, it is automatically fed into the public grid. However, the user does not receive any compensation for the excess electricity, although according to the EEG 2023 he is entitled to the feed-in tariff of 8.2 cents. Provided that the photovoltaic system is less than ten kWp (kilowatt peak). If the solar system is over ten kWp, the owner receives 7.1 cents per kilowatt hour. However, if all of the electricity from solar is fed into the public grid, a surcharge of 4.8 cents per kilowatt hour is paid.

In this case, of course, it doesn't happen without major bureaucratic effort. The network operator must be informed about the claim for the feed-in tariff. In addition, an electricity meter must be installed to measure the solar power fed in. The cost for this is usually more than 100 euros. Of course, an annual measuring point fee of around 20 euros must also be paid. However, if the plug-in solar systems have an output of more than one kilowatt, installing a modern measuring system is a good option. The cost per year is around 60 euros. In order to receive remuneration for the electricity fed in for the current year from the network operator, the quantity fed in must be determined and reported to the network operator by the end of February of the following year.

However, if the owner of the balcony power plant is willing to forego the remuneration and does not want to “give away” the electricity generated but instead wants to use it himself, then expanding the balcony power plant to include a storage facility is an option. The excess energy is then stored in these for later use. Such memories are available on the market, but they are quite expensive. It is therefore important to consider whether this investment is worthwhile in a 600-watt balcony power plant, where the surplus electricity is quite manageable.

Plug-in solar system – costs, subsidies and amortization

A balcony power plant can be purchased for between 500 euros and 1,400 euros. The VAT of 19 percent has been waived since January 1, 2023 when purchasing such devices. This means a saving of 19 percent of the purchase price for the buyer.

Unfortunately, in 2023 there will be no funding program for balcony power plants that applies throughout Germany. However, individual federal states encourage the purchase of small plug-in solar systems. Many municipalities also support these solar systems with subsidies. However, the funding conditions and funding rates can vary from municipality to municipality.

Example calculation regarding the amortization of a balcony power plant:

A 600-watt balcony power plant that cost around 800 euros pays for itself after around two and a half years, namely:

800 kilowatt hours annual yield x assumed 0.40 euros per kilowatt hour = 320 euros -> 320 euros x 2.5 years = 800 euros total savings

It can be assumed that balcony power plants will pay for themselves even more quickly in the future. The reason for this is the sharply rising electricity prices.

Criteria to consider before purchasing

Before and when purchasing a balcony power plant, which is usually offered as a complete package, some criteria and the size of the balcony should be considered. These are:

• Before purchasing a mini PV system, it is important to know whether the house's electrical installation is older. If the condition is not known, it should be checked in advance by an electrician.
• It should also be clear what output the desired plug-in solar power plant should have. It should be noted that a balcony power plant in Germany, if the installation is to be carried out on your own initiative, must not exceed an output of 600 watts. The installation of plug-in solar systems with a higher output may only be carried out by an electrician. In these cases, an electricity meter with a backstop is also required.
• It is also important that the components of the complete package such as the PV module, inverter, plugs, sockets and cables have the CE markings. The TÜV seal and other recognized certificates also stand for high quality standards.
• The guarantee is also an important aspect. The guarantee for the PV module should be at least 25 years and for the inverter ten to 12 years.
• It is also important that you seek individual advice from a reputable provider or expert seller before purchasing. There is also the option to find out more about plug-in solar systems on the relevant website. In addition, the website provider should have all the necessary forms required for installation and registration as well as the product sheets available for download. Another positive aspect would be if the seller took over the entry of the balcony power plant in the market master data register and the registration with the network operator.
• Don't forget to plan the budget for the desired plug-in solar system. It is important to know how much money should be invested in the mini PV.
  

Short conclusion

With a balcony power plant, private individuals and tenants have the opportunity to generate electricity from solar energy on their own balcony. If this is used during the day, electricity costs are reduced. Anyone who takes various aspects into account before purchasing, such as the performance of the mini photovoltaic system, the balcony size, the costs and the quality of the components and receives expert advice, will find the optimal balcony power plant that meets their individual needs. A plug-in solar system used over the long term not only leads to energy savings, but also contributes to environmental protection.