Germany’s Marktstammdatenregister and grid-connection arrangements are distinct. Confirm each task and keep its evidence.
Identify the separate processes
The Bundesnetzagentur provides the Marktstammdatenregister for energy-market registrations, including guidance for solar and storage. Separately, your grid operator deals with connection arrangements. A completed task in one process is not proof that the other is finished.
Put responsibility in writing
Ask whether the installer assists with registration or whether you must complete it. If a battery is included, ask how it is handled. Use the official portal for the current requirements and deadlines; do not rely on a date copied into an old sales leaflet.
Build a handover folder
Keep equipment details, commissioning information, registration confirmations and grid correspondence together. Check that the details match the installed equipment. If something is unclear, follow up with the responsible organisation rather than assuming that a working system means all administration is complete.