A balcony power plant (Balkonkraftwerk) has to be entered in the German Market Master Data Register (Marktstammdatenregister), according to the Verbraucherzentrale, and this expressly includes small plug-in solar devices (Steckersolargeräte). Many operators know little about this duty, and registration is where mistakes are easiest to avoid. This guide explains what the register is, which details you need and what happens if a system is not entered.
Short answer: Yes, plug-in solar devices are entered in the register of the Federal Network Agency (Bundesnetzagentur) in the same way as large photovoltaic systems. Registration is done online and asks, among other things, for the number of modules, the output and the commissioning date. According to the Verbraucherzentrale, anyone who is not registered loses the EEG feed-in remuneration and risks a possible fine. As a general deadline, section 5(5) MaStRV names one month after commissioning. Last updated: November 2026.
The most important points in brief
- Plug-in solar devices belong in the Marktstammdatenregister, even if you receive no remuneration.
- The Federal Network Agency is responsible, and registration takes place exclusively online.
- You create a user account once and confirm the name and address of the operator.
- A battery storage unit has to be registered separately.
- You report changes, and you delete the entry when the modules are permanently removed.
What is the Marktstammdatenregister?
The Marktstammdatenregister is the central database of the Federal Network Agency for electricity generating plants and storage units. It records plants with technical and location details, so that the authorities responsible for networks and energy have a complete picture of generation. For you as an operator, this means that a plant that generates electricity must be reported, however small it is.
The Verbraucherzentrale expressly points out that plug-in solar devices must be registered like large photovoltaic systems. The article does not mention any simplified exemption for balcony power plants.
That registration plays a role for the EEG feed-in remuneration is already clear from the consequence of a missing registration that the article describes.
Which details do you need for registration?
Registration has two parts. First you create your user account and confirm the name and address of the operator. Then you describe the system itself. The following table shows the details that the procedure asks for.
| Detail | What it refers to |
|---|---|
| Operator | Name and address, confirmed during registration |
| Number of modules | How many modules the system comprises |
| Output | The output of the system that you enter |
| Commissioning | The date on which the system went into operation |
| Battery storage | Whether a storage unit is used, which must then be registered separately |
Have these details ready before you start. The data sheet of the modules and your invoice help you to transfer the figures correctly. Unclear values lead to queries later or to an entry that you have to correct.
By when must you register the system?
Under section 5(5) sentence 1 of the Market Master Data Register Ordinance (MaStRV, gesetze-im-internet.de, retrieved on 2 November 2026), units and EEG plants must be registered within one month after commissioning. The Verbraucherzentrale gives the same one-month period as the general rule for new systems. Section 5 MaStRV, in the text retrieved, contains no separate deadline for plug-in solar devices. Whether special rules apply to them is something to ask the Federal Network Agency. You may also register before commissioning. For older systems, the article recommends registering promptly.
If you are just setting up your balcony power plant, registering before the first start is the simplest route. You avoid delays and do not have to keep track of a deadline date.
What happens if you do not register the system?
According to the Verbraucherzentrale, anyone who does not register loses the remuneration under the EEG. A fine under section 95 of the Energy Industry Act (EnWG) may also apply. The article further notes that systems without remuneration must still be registered. The duty therefore does not depend on whether you receive money for the electricity you feed in.
The loss of remuneration hits operators who expect payment particularly hard. The duty to register, however, applies regardless of whether you receive a remuneration, as the article explicitly states.
How do you proceed with registration?
The following list summarises the process as the Verbraucherzentrale describes it. The order follows the registration, but you do not have to complete all steps on the same day.
- Create a user account in the Marktstammdatenregister once and confirm the name and address of the operator.
- Enter the system with the number of modules, the output and the commissioning date.
- State whether a battery storage unit exists, and register it separately.
- Report every later change to the system.
- Delete the entry when the modules are permanently removed.
What about the battery storage?
According to the article, a storage unit used with a plug-in solar device must be recorded separately in the register, just like any other storage unit. Registering the storage unit therefore supplements the entry for the system and does not replace it. If you add a storage unit later, complete the entry promptly.
The storage entry is a separate duty and is not covered by registering the system. How a storage unit is connected technically in the household is a separate question. This guide only covers the registration duty, not installation or output questions.
Why you should report changes promptly
The entry is meant to reflect the actual state of your system. If you add modules, change the output or add a storage unit, you must report it. If the modules are permanently removed, you delete the entry. After such changes an outdated entry no longer matches the system you actually operate.
It helps in practice to keep a short note with the commissioning date, the number of modules and the output. If you later change the set-up, you can find the details immediately and do not have to reconstruct what applied at the time.
Where can you get help with registration?
The Federal Network Agency runs the Marktstammdatenregister and answers questions about registration. According to the Verbraucherzentrale, you can reach the hotline during office hours on 0228 14-3333. A contact form is also available.
A question about registration is something different from a question about technology or tenancy law. For tenancy questions, the guide on balcony power plants in rented flats gives an overview. For technology and output, an electrical installer or the manufacturer is the better contact.
Frequently asked questions
Do I have to register even without a feed-in remuneration?
Yes, according to the Verbraucherzentrale, systems that receive no remuneration must also be entered. Giving up the remuneration therefore does not release you from the duty.
Who is responsible for the registration?
The Federal Network Agency is responsible, and registration takes place online. If you have questions about the entry, you can contact the hotline or the contact form that the article lists during office hours.
What if I have made a mistake?
Changes to the entry must be reported, and that includes corrections. After registration, check the number of modules, the output and the date again and report any deviations promptly.
Does the duty also apply to small devices with few modules?
The article names plug-in solar devices in general as subject to registration and contains no exception for small systems. You should therefore assume that the duty applies.
How to proceed now
- Prepare your documents: number of modules, output, commissioning date and details on any storage unit.
- Set up your account in the Marktstammdatenregister and confirm the operator.
- Enter the system, ideally before or shortly after commissioning.
- Note dates for changes and for deleting the entry.
Related guides
- Climate, energy and costs 2027: The overview for tenants and students
- Balcony power plant in a rented flat: Can the landlord say no?
- Calculating electricity costs: From appliance to monthly amount
- Saving Electricity as a Student: Energy and Utility Costs
Sources: Verbraucherzentrale: Marktstammdatenregister, what you need to know about solar systems and more, status 23 July 2026 (in German). Market Master Data Register Ordinance, section 5 MaStRV, registration (in German, retrieved on 2 November 2026).
Last updated: November 2026. This guide is general information, not individual advice.
