NGEN and NextGrid Energy open Croatia’s first large standalone battery energy storage system – 60 MW / 120 MWh

A storage system that keeps grid frequency stable

At full power, the system can draw electricity from the grid or feed it back for around two hours, responding to grid needs almost instantly. It consists of Tesla Megapack XL battery units connected to the 110 kV transmission grid.

Since September 2026, its entire capacity has been dedicated to automatic frequency restoration reserve (aFRR) under a contract with HOPS. The operator uses this reserve to balance deviations between electricity generation and consumption in real time, keeping grid frequency stable.

Fully automated operation with the NGEN platform

NGEN played a key technological and operational role in delivering the project. For BESS Šibenik, it developed the software platform and control system that enable fully automated operation.

The platform continuously monitors market and grid conditions and optimises the system’s operation every 15 minutes. This allows the storage system to participate in balancing markets and respond to the grid operator’s requests in real time. NGEN’s key role was also highlighted at the opening by Željko Šmitran, Director of NextGrid Energy.

“Together with our partner NextGrid Energy, we developed and delivered BESS Šibenik, the first large standalone battery system connected to the Croatian transmission grid. The project will contribute to the stability of the power system and to greater integration of renewable energy sources. I believe Šibenik marks the beginning of our continued cooperation and of new projects that matter for the energy future of Croatia and the region,” said Roman Bernard, CEO and co-founder of NGEN Group.

A merchant model without guaranteed revenues

BESS Šibenik operates without guaranteed revenues. Its income depends on demand for flexibility services, and the market risk is borne entirely by its owners and investors. Because solar and wind generation depends on the weather, battery storage becomes increasingly important for balancing generation and consumption as their share grows.

The project received grant funding from the EU Modernisation Fund and equity investments from the European Bank for Reconstruction and Development (EBRD), Raiffeisen pension funds and IE-ENERGY.

Further projects in Croatia and the region

NGEN already operates utility-scale battery storage systems in Slovenia, Austria and Poland. NGEN and NextGrid Energy hold equal stakes in NGEN Smart Energy Systems, which develops and manages flexible energy resources in Croatia. The partners are already planning new energy storage and flexibility projects in Croatia and across Central and South-Eastern Europe.