Plug-In Solar (Balkonkraftwerk) in Cologne: Register Only in the Marktstammdatenregister, RheinNetz Meter Rules and the Spent City Grant

The Short Version for Cologne

Plug-in solar is one of the few things where Germany got simpler. In Cologne, RheinNetz is the grid operator, and its Balkonkraftwerk page says to register in the Marktstammdatenregister and that a notice to the grid operator is no longer required. The MaStR passes your data on to the grid operator automatically, according to its FAQ.

Registering Step by Step

The official registration guide describes two steps.

1. Create a user account. Enter your data, confirm the email, and the account is active.
2. Register yourself as operator and the device. You need the location, the name of the unit, the date of commissioning, the total power of the modules, the inverter power and the meter number. The meter number is confidential and not published.

The date of first commissioning is, according to the MaStR, the moment the device first feeds alternating current into your household network, which is usually when you first put the plug into a socket. RheinNetz lists the same details: connection address, technical data, module and inverter power, manufacturer type, meter number and the operator’s contact details. The meter number identifies your connection point and is on your meter, your last bill, or the handover record if you just moved in. Download the registration confirmation from your MaStR account, since it is the proof some funding programmes ask for.

The Meter

RheinNetz says that since May 2024 you may run a plug-in device with an analogue meter with a rotating disc, and that the meter operator will replace it with a digital meter. Even though unintended feed-in is not paid, it has to be measured by a bidirectional meter. You are allowed one plug-in device per meter. If your device is bigger than 800 W, it is no longer a mini system: it must be registered as a normal generating plant through RheinNetz’s portal and process, and new meters are ordered through an electrical installer. For meter readings in general, see our page on submitting your electricity meter reading.

The plug itself is a separate question from registration. The federal economics ministry’s short guide says that under the product standard DIN VDE V 0126-95:2025-12, a connection with an ordinary household plug and added protective measures is standard-compliant for module power up to 960 W, while modules above 960 W and up to 2,000 W still need a special feed-in plug device. Check the plug type on the box before you buy.

Tenants and Owners

§ 554 BGB gives a tenant a claim that the landlord permits changes serving the generation of electricity with plug-in solar devices. There is no claim if the change is not reasonable for the landlord even considering the tenant’s interests, and the tenant may offer a security. Agreements that disadvantage the tenant are void. In practice:

• Write to the landlord before you mount anything, describing where and how.
• Keep the mounting safe, since the city’s own leaflet requires a windproof installation for grant purposes.

Owners in a condominium have a parallel right in § 20 WEG: each owner can demand reasonable structural changes serving plug-in solar devices, and the community decides on how to carry them out. The text excludes changes that fundamentally alter the building or unfairly disadvantage an owner. For the conversion of rented flats into condominiums, see our page on the ten-year protection after conversion.

The Cologne Grant, and Why It Is Closed

Cologne had one of the clearer local incentives. The city’s PV programme paid 150 euros per residential or commercial unit for a plug-in set, and 300 euros per residential unit for holders of the Köln-Pass. The set had to have 600 to 2,000 Wp of modules and 600 to 800 W of inverter output, one device per unit, with no home-built devices and no battery storage for plug-in devices. The city’s leaflet required the MaStR confirmation as proof, a photo of the installed device and, for the higher amount, a valid Köln-Pass, with the application made in the city’s online funding portal.

But in a press release of 28 September 2026, the city announced that the funds of the PV programmes were exhausted. No further applications are accepted, and the applications received until 27 September 2026 use up the 8 million euros available for 2026. The programme guideline runs until 31 December 2026 and says there is no legal claim to a grant. The city adds that, because of the budget situation, a continuation is currently not planned. So the honest advice is: do not buy a device in the expectation of a grant. Look at the city page again in case a new programme appears, and if one does, read the purchase-date rule before you buy.

Step by Step

1. Check your meter: one device per meter, and your meter number is needed.
2. If you rent, ask the landlord in writing, citing § 554 BGB.
3. Buy a set within the limits of 800 W inverter output, and mount it securely.
4. Register in the MaStR when you first plug it in, and keep the confirmation.
5. Let the meter operator swap an old meter, and do not feed in more than your own use.
6. Check the city page for a new grant before spending money you hope to get back.

Compliance Note

This page summarises information from RheinNetz, the Marktstammdatenregister, the Civil Code, the Wohnungseigentumsgesetz and Stadt Köln as read in October 2026. Limits, rules and funding change often. It is not legal or technical advice. For wiring questions, ask a qualified electrician.