A groundbreaking milestone in European clean energy infrastructure is underway with the planned construction of a 1 GW/4 GWh battery energy storage system – the largest of its kind in Europe – at the former Jänschwalde power station site in eastern Germany. LEAG Clean Power GmbH, the low-carbon subsidiary of German energy company LEAG, in partnership with U.S. energy storage technology provider Fluence Energy GmbH, a German subsidiary of Fluence Energy are developing the project. The project also marks a major deployment of utility-scale storage that will help stabilize the grid, absorb high volumes of renewable generation and provide essential flexibility services as Germany transitions away from coal-fired power. Fluence & LEAG’s project will also complement grid services to be offered by TotalEnergies & Allianz battery storage portfolio in Germany that expects commissioning through 2028 after recently signing a US$583 million partnership.
Additionally, the battery system’s scale, at 4 GWh of storage capacity, positions it not only as Europe’s largest single battery project to date, but also as Fluence’s largest single installation globally using its Smartstack battery platform.
Team Behind Europe’s Largest Battery Storage Project by Fluence and LEAG at 1 GW/4 GWh
LEAG Clean Power GmbH as developer and owner
- Responsible for overall project permitting, land use planning at the Jänschwalde site, grid connection strategy and community outreach.
Fluence Energy GmbH as technology Provider and system integrator
- Fluence will deliver the battery energy storage system technology, including modular battery units and power conversion systems. Will also serve as technical partner on grid integration and controls.
German Transmission System Operators (TSOs)
- Serve as approvers and facilitators of interconnection at high-voltage network level, crucial for a system this size. Likely involved parties include national network operators such as 50Hertz, TenneT, Amprion and TransnetBW.
Brandenburg State Authorities & Local Municipalities
- Involved in regulations and permitting supporting planning reviews, land use approvals, and socio-economic impact assessments for the project’s siting in the former industrial region of Jänschwalde.
Largest Battery Storage Project in Europe at 4 GWh, to be Built in Germany by Fluence and LEAG
Reported November 7, 2025 – LEAG Clean Power and Fluence have announced a joint venture to build the largest battery energy storage system (BESS) project in Europe with a 1 GW/4 GWh capacity in Janschwalde, Germany. The 1 GW battery storage project will use Fluence’s Smartstack platform. The Janschwalde battery storage project will be up against mega installations like the 700 MW/2800 MWh GIGA Green Turtle battery park in Belgium.
Factsheet for the Largest Battery Storage Project in Europe: GigaBattery Janschwalde 1000
Location: Janschwalde in Lusatia, Germany.
Developers: LEAG Clean Power and Fluence Energy
Capacity: 1 GW of power and 4 GWh of storage capacity.
Technology: Fluence Smartstack modular battery and PCS system.
Status: Final approvals and construction pending.
Estimated Timeline: Permitting in 2026. Construction through 2028.
Significance: Largest battery project in Europe. Also, a major milestone in Germany’s energy transition.
Timeline for the Largest Battery Storage Project in Europe
2024: LEAG’s GigawattFactory strategy publicly expanded. Large renewable and storage plan also announced.
November 2025: LEAG and Fluence partner for the largest battery storage system in Europe with 1 GW/4 GWh capacity to be built in Germany.
Q2 2026: Final permitting and planning expected.
2027-2028: Construction and commissioning of the storage facility.
Outlook on Europe’s Largest BESS in Germany by LEAG and Fluence
Germany’s transition from coal towards renewables creates a need for large scale battery systems to store excess wind and solar output. The battery systems are also going to be key in stabilizing the grid. They are also important for the reuse of existing infrastructure like transmission lines and brown coal power plant sites. Germany is also home to a 1 GW/2GWh battery storage installation by ADS-TEC that expects completion in 2029.
LEAG’s GigawattFactory initiative in Lusatia also proves to be an important regional transition program. The initiative aims to convert legacy coal sites into renewable hubs. These will incorporate wind, solar, hydrogen and storage projects. The 4 GWh battery project set to be the largest in Europe is emblematic of this shift, a renewable momentum also evident as INTEC expands its German portfolio with a 50 MWp Lower Saxony solar deal. It is expected to make scalability flexible, support higher renewable penetration and encourage industrial development in a former coal region. The same transition is being witnessed across former nuclear sites as well, for instance with Vattenfall’s 254 MW BESS project.
The involvement of Fluence, who is a global leader in storage systems, also underscores the how batteries are becoming a cornerstone of Europe’s energy transition infrastructure.
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