Market Master Data Register 2026: registering a rooftop system step by step
A rooftop system must be in the Market Master Data Register within one month of commissioning. Without the entry, the operator owes the grid operator €10 per kW and month, which is €100 a month for 10 kWp.
Checked by Radif Partners · Editorial policy · How we calculate
What a late registration can cost
Payment to the grid operator
€60
| Rate | €2 per kW and month |
| without registering it would be | €300 |
| Basis | § 52 EEG 2023 |
The Market Master Data Register (Marktstammdatenregister, MaStR) of the Federal Network Agency is the official list of every power generator in Germany, from a balcony kit to a wind farm. If you operate a rooftop PV system, you must enter yourself as the operator and the system as a unit, within one month of commissioning (section 5(5) MaStRV). A battery is a separate unit and is registered as well. Registration is free; have the commissioning report and data sheets to hand. The grid operator then checks the entries. If you miss the deadline and have not reported annual data to the grid operator either, section 52 EEG makes you owe €10 per kilowatt and month or part month. Once you catch up, the amount drops retroactively to €2. For a 10 kWp system that was missing for three months, that is €60 instead of €300. The grid operator may offset the sum against your feed-in payments.
When the clock starts
The deadline starts at commissioning, not at purchase and not at the meter change. For PV, that is the moment the system first generates power after being permanently installed; the date is on your installer’s commissioning report (Inbetriebnahmeprotokoll). From that day you have one month to enter operator and unit in the Market Master Data Register (section 5(5) MaStRV). This applies regardless of when the grid operator fits the bidirectional meter.
What to have ready
- the commissioning report with the date and installed panel capacity in kWp,
- the inverter data sheet with its rated output in kW,
- the number of panels, main orientation and tilt of the roof face,
- the address or land parcel of the building and the name of your grid operator,
- for a battery: usable capacity in kWh, charge and discharge power in kW,
- whether you chose surplus or full feed-in.
The installed panel capacity is the gross output, the inverter rating the net rated output. The register asks for both separately; mixing them up triggers a query from the grid operator.
Registration in five steps
Create a user account
On the register’s home page you create a user account with an e-mail address and password and confirm the link in the confirmation e-mail. The account is also how you enter changes later on.
Register yourself as operator
Next you register yourself as a market actor in the role of system operator (Anlagenbetreiber), as a private individual with your personal details. The register gives you a MaStR number of your own.
Enter the solar system as a unit
Then you create the generating unit: energy source solar radiation, located on a building, site, commissioning date, capacities, panels, orientation and feed-in type. The unit receives a second MaStR number, which you pass on to the grid operator; many need it to pay the feed-in tariff.
Add the battery
A battery is created as a separate storage unit and linked to the solar system. This applies to AC- and DC-coupled batteries alike.
Wait for the check and pass on the number
After submission, the grid operator checks the entries in the register. Your duty is fulfilled once complete data has been submitted; you answer any queries through the same account. A plug-in solar device follows a shorter route with fewer fields, described on registering plug-in solar.
What a missed deadline costs
Section 52(1) no. 11 EEG makes operators pay the grid operator if the data required for registration was not submitted and no billing data was reported under section 71(1) no. 1 EEG either. The amount is €10 per kilowatt of installed capacity for each calendar month in which the breach exists in whole or in part. If you catch up, it drops retroactively to €2 per kW and month from the start (para. 3 no. 1).
| Case | not registered | registered later |
|---|---|---|
| 10 kWp, 3 months | €300 | €60 |
| 10 kWp, 12 months | €1,200 | €240 |
| 25 kWp, 6 months | €1,500 | €300 |
For comparison: on the national average, the same 10 kWp system earns about €55 of feed-in tariff a month. A single month without an entry at the full rate therefore costs more than the system is paid in that time. The grid operator may offset the payment against your tariff claims and instalments (para. 6); the claim lapses at the end of the second calendar year after the breach. For older systems, too, only section 52 has applied to registration breaches since 1 January 2023 (section 100(9) EEG).
Mistakes that trigger queries
Most grid operator queries have a handful of causes. Often the register shows the date of the meter change instead of the commissioning date; the report is what counts. Just as often, panel capacity and inverter rating are swapped, so a 10 kWp system appears as 8 kW. A third classic is the duplicate unit: the installer creates it with a power of attorney and the operator creates it again a few weeks later. Agree beforehand who registers. Finally, the battery is often forgotten because it sits in the same housing as the inverter. Each of these errors can be corrected through the account, and as long as the data was submitted on time, none of them leads to a section 52 payment.
After the entry
Registration is not a one-off. If anything changes, such as extra panels, a new battery, selling the house or decommissioning, enter it through your account; after a change of owner, the new operator registers themselves. A system without export must also be entered, as the page on zero export explains. The register has no bearing on tax; the rules there are under solar PV and tax. The Federal Network Agency answers common questions on its solar page.