The mandatory installation of solar systems on buildings now applies in ten German federal states, following the introduction of corresponding regulations in five more states. Schleswig-Holstein will follow suit next year.
On 01.01.2025, Section 32a of the Lower Saxony Building Regulations, adopted in December 2023, comes into force, introducing stricter solar roof requirements.
The solar requirement applies to all buildings constructed from 2025 onwards with a roof area of at least 50m2.
Solar panels must then cover 50% of the total roof area, provided this does not conflict with another public-law obligation and is technically feasible and economically viable.
A solar thermal system does not provide an exemption from the requirement. However, the area it occupies is deducted from the required area.
Installation is technically impossible on thatched or glass roofs, as well as on existing buildings with insufficient load-bearing capacity.
Systems that do not pay for themselves over a typical service life of 20 years are considered economically unviable. Depending on electricity demand, this does not necessarily rule out north-facing roofs!
We recommend having a solar adviser carry out a site-specific analysis. Our solar advisers use PV-Sol or Aurora to prepare an analysis, including an economic viability calculation. The PV system is designed to meet the anticipated energy demand. Feeding too much surplus electricity into the grid reduces economic viability. The analysis is included in the system documentation.
The party commissioning the construction is responsible for compliance.
The solar roof requirement has applied to newly constructed commercial buildings since 2023 and to all new public buildings since 2024. Even before this, all new buildings had to be constructed in a way that would allow a photovoltaic system to be retrofitted without additional structural reinforcement. Since the start of 2025, the solar requirement has also applied to all new publicly accessible car parks and parking decks with more than 25 spaces.
North Rhine-Westphalia has a regulation similar to that in Lower Saxony. Section 42a of its state building regulations stipulates that a solar system must be installed if the building application was submitted after 1 January 2025. This is subject to the building having a usable floor area of more than 50 square metres. A solar requirement for the refurbishment of commercial roofs is also planned for 2026.