More than 4,000 sq kms of technically suitable rooftop space on German buildings carries a potential for around 400 GW solar PV capacity to be installed, according to a report commissioned by Agora Energiewende.
This, it explains, roughly corresponds to the country's overall expansion target for photovoltaics of 400 GW by 2040 under the Renewable Energy Sources Act (EEG) (see Germany's Bundestag Clears Easter Package).
With its advantage of generating solar power on the site of consumption, rooftop solar can make a significant contribution to Germany's climate goals; however, these systems remain more expensive than ground-mounted PV systems due to complex installation and small yield areas.
Agora commissioned greenventory GmbH to carry out aerial photography and artificial intelligence (AI) supported analysis to bring in clarity about the contribution of rooftop PV in Germany at a zip code level, differentiated by the size of the roof and the building use.
Authors explain that this makes it easier to identify potential locations and develop PV expansion strategies for different building uses. These range from buildings used for transport and logistics, business and commerce, leisure, manufacturing facilities, agricultural setups, and residential structures.
Pointing at the federal states not having yet exploited their rooftop potential, authors of the study list buildings that can help get there beyond residential buildings that carry the most potential so far.
Large roofs with more than 500 sq. m. area can especially be taken into consideration as these offer an opportunity to install more PV with little planning effort, thereby reducing investment costs. These also come in handy in times when ground-mounted PV expansion is encountering land-use conflicts and acceptance problems.
According to the report writers, "Theoretically, a quarter of the total potential of rooftop photovoltaics can be realized on these houses, which make up around six percent of the buildings. These are primarily production halls, residential buildings as well as buildings in the retail and commercial sectors."
To encourage rooftop solar installations, Germany recently announced amending grid connection rules for smaller electricity systems of up to 500 kW capacity, with an eye on commercial and private rooftop systems (see Germany Speeding Up Rooftop Solar Deployments).