Battery storage systems in outdoor areas - current classification in accordance with § 35 BauGB

Briefing

The permissibility of battery storage systems in outdoor areas was characterized by considerable uncertainty for a long time. Battery storage systems were not expressly regulated in the Building Code (BauGB) and their classification as privileged projects was inconsistent in administrative practice. In some cases, privileged treatment as a public power supply facility pursuant to § 35 (1) No. 3 BauGB and in some cases this was expressly denied.

With the most recent amendments to § 35 (1) No. 3 BauGB, the legislator has introduced independent privileges for battery storage systems for the first time. The new regulation is the result of a short-term and quite turbulent legislative process.

Legislative starting point and structure of the new regulation

The starting point for the reform was the realization that battery storage systems play a central role in a flexibilized energy system, without their classification under planning law having been clearly defined to date. In the meantime the German Bundestag had even decided on November 13, 2025 to grant largely unrestricted privileges to stand-alone projects. However, after strong headwinds, particularly from the federal states and local authorities, another Bundestag resolution immediately followed on December 4, 2025, which now differentiates the legal situation. It is expected that both resolutions will come into force on January 1, 2026, meaning that the unrestricted regulation will no longer apply and will instead be immediately overlaid by the restricted version.

The version of § 35 (1) No. 3 BauGB then in force distinguishes between two independent facts for battery storage facilities in outdoor areas, each of which is linked to different functional and spatial requirements. The law then does not contain any general privileges that are independent of location.

Battery storage in a spatial-functional context with renewable energy generation systems

According to the new § 35 (1) No. 11 BauGB, battery storage systems that are spatially and functionally connected to an existing renewable energy plant are considered privileged. In particular, this includes storage systems that are assigned to a wind energy system or a ground-mounted photovoltaic system and are intended to at least partially absorb its electricity.

The legislator uses the concept of spatial-functional connection known from public planning law. A technically and economically viable connection is required, although the explanatory memorandum to the law leaves the details open. However, a subordinate or serving function of the storage, as previously required for so-called ‘mitgezogene Privilegierung’, is not required.

It is also of practical importance that the privileged storage system does not necessarily have to have been approved on the same planning law basis as the production plant. Battery storage systems that are connected to systems that were themselves built on the basis of a development plan may also be eligible for the privileged status. This significantly expands the scope of application compared to previous constructions of the "mitgezogene Privilegierung".

However, ambiguities remain with regard to the definition of the spatial reference and the question of what stage the production plant must be at in order to be considered "existing". The legislative materials argue in favor of basing this on the time of approval of the production plant in order to avoid accidental results for example due to construction delays.

Independent battery storage in the proximity to energy infrastructure

In addition, § 35 (1) No. 12 BauGB (new version) grants a privilege for stand-alone battery storage systems without direct allocation to a renewable energy plant. However, this option is linked to several cumulative requirements.

Firstly, a minimum capacity of the storage system of 4 MW which, however, will be achieved by the vast majority of stand-alone projects without any problems. It is also necessary that the storage location must be no more than 200 meters from the boundary

of a substation at the extra-high to high voltage or high to medium voltage level or
an operating or decommissioned power plant with a rated electrical output of at least 50 MW.

It is noteworthy that the law does not expressly require transformer substations to be in operation or approved nor does it require them to be substations of the grid operator. This means that substations planned together with the battery storage system may also fulfill the proximity requirement, which would significantly expand the scope of application of this variant. It also remains unclear how the distance of 200 meters is to be determined. The genesis of the standard and legislative materials speak in favour of a 200-metre distance from property boundary to property boundary; however, a 200-metre corridor is also being discussed, as known, for example, from the privileged approval of ground-mounted PV systems in accordance with § 35 (1) No. 8 BauGB.

In addition the privilege pursuant to § 35 (1) No. 12 BauGB (new version) is subject to an area-related upper limit at municipal level. The total area occupied by privileged battery storage facilities, including ancillary facilities, may not exceed 0.5% of the municipal area per municipality and may not exceed 50,000 m². The limit that is reached first is decisive. This limit means that the realization of larger battery parks in outdoor areas is in fact severely restricted and a "greyhound race" for the reservation of areas per municipality is likely to arise. It should also be noted that the usual calculation of floor space in accordance with the BauNVO should not be applied, but that open spaces and access routes, for example, must also be taken into account.

Legislative objectives and control approach

The new regulation clarifies that although the legislator recognizes battery storage systems as system-relevant/ critical infrastructure, it wants to deliberately steer their siting in outdoor areas. Storage facilities that are either integrated into existing generation structures or are linked to existing energy industry locations are given priority.

At the same time, performance, distance and area criteria are intended to prevent uncontrolled use of outdoor areas and the widespread establishment of large storage parks. The privileged status thus becomes an instrument of spatial control, not a blanket facilitation. In particular for large BESS projects that cannot be accommodated within an area of 5 ha, the possibilities offered by urban land-use planning and planning approval are likely to become increasingly attractive in the future.

Classification compared to the legal situation before the reform

Prior to the introduction of the new legal provisions, battery storage facilities in outdoor areas were not expressly privileged. In some cases, approval practice resorted to § 35 (1) No. 3 BauGB and classified storage facilities as installations for the public power supply. This regularly required a particular location and led to widely divergent results across Germany. In several federal states, there were also administrative requirements that fundamentally rejected the privileged treatment of battery storage systems.

Against this backdrop, the new regulation creates an independent assessment standard under federal law for the first time, even if this is associated with restrictions in the most recently adopted version.

Practical significance and remaining questions of interpretation

The new privileges lead to a clearer system but leave numerous questions of interpretation unanswered. This concerns in particular:

the determination of the spatial-functional connection,
permissible performance values and operating concepts for co-located projects,
the specific measurement of 200-meter distances and
the calculation and updating of municipal area quotas.

In a motion for a resolution adopted on December 19, 2025, the Federal Council (Bundestag) draws attention to the numerous questions of interpretation and suggests that the standard be tightened up again. Further amendments may therefore be expected in the new year.

Regardless of admissibility under construction planning law, battery storage facilities remain subject to other public law requirements, in particular nature conservation and species protection law, water- and fire protection law and must also continue to overcome the "bottleneck" of grid connection. Only the application in approval practice will show to what extent the new regulation actually contributes to more planning security and an acceleration of storage projects.