A Fraunhofer IEE study, commissioned by BSW-Solar, identifies 150 GW of additional PV potential in Germany with the addition of BESS across 1,313 substations
Batteries can shift solar output away from periods when transformers reach their operating limits, according to the study
The modeled 150 GW potential would require around 60 GW/240 GWh of battery storage under the study’s reference scenario
Germany could potentially accommodate 150 GW of additional solar PV through the use of smart battery storage at existing substations, according to a Fraunhofer Institute for Energy Economics and Energy System Technology (IEE) study, commissioned by the German Solar Association (BSW-Solar).
Currently, the country targets to achieve 215 GW of solar PV capacity by 2030. It exceeded 129 GW at the end of August 2026 (see Germany’s August 2026 Solar Installations Exceed 1.6 GW).
The study identifies this technical potential across 1,313 rural substations with high renewable generation. It estimates that around 60 GW/240 GWh of battery storage would be needed under its reference scenario.
The analysis starts from the observation that transformers do not operate at their rated capacity throughout the year. Moreover, electricity demand, wind generation and solar output vary by time, leaving transmission capacity unused during many periods.
Intelligently controlled large-scale battery energy storage systems (BESS) located directly at a substation could then charge when local solar generation pushes power flows toward the transformer limit. It could then release the stored electricity later. This, according to the analysts, would allow more efficient use of existing transformer capacity, relieving the load on the substations.
As a result, on an annual average, only about one percent of the additionally generated solar power would need to be curtailed due to transformer capacity limits, according to the study.
The analysts offer this conclusion after analyzing data from 20 transformers at 13 substations operating in the networks of Pfalzwerke Netz and Westnetz. The transformers had capacities ranging from 15 to 80 MVA, with simulations based on hourly data for 2025.
“If storage systems charge where and when peaks in solar power generation occur, they can specifically alleviate grid bottlenecks and enable the integration of additional solar power. This could lead to savings of billions in grid expansion costs, among other benefits,” said Carsten Körnig, CEO of BSW-Solar.
The association says the findings are relevant to the Bundestag’s proposed Grid Package which aims to better coordinate renewable energy, storage and grid expansion. BSW-Solar argues that the government must ensure that existing grid capacity is used more efficiently alongside further grid expansion.
It also wants the administration to designate grid bottleneck areas only after grid operators have implemented digitalization of medium- and high-voltage networks and conducted feasible storage tenders.
