Serbia’s 66 MW Kostolac wind farm remains offline despite the completion of construction, with outstanding issues between state-owned utility EPS and turbine supplier Siemens Gamesa continuing to delay the project’s formal handover and commercial operation.
The EUR 145 million project has all 20 turbines installed and connected to the grid, and it has already generated electricity during trial operations. However, regular commercial operation has yet to begin, almost two years after the project’s original completion deadline of October 2024.
EPS said in June that Siemens Gamesa had not fulfilled all of its contractual obligations, leading the utility to decline signing the Taking-Over Certificate. A joint statement issued the following month said the project engineer had issued the certificate on 6 March 2026, confirming that construction and installation works had been completed. The companies said they would continue working together to resolve the remaining issues.
Trial operation at Kostolac began in November 2025, with all 20 turbines connected by the end of the year. The wind farm delivered 37.37 GWh of electricity to the grid by 22 February 2026, before generation was suspended. No date has been announced for the plant’s return to operation.
Once fully operational, Kostolac is expected to generate approximately 115 GWh of electricity annually, enough to cover consumption equivalent to around 30,000 households. Its completion would also represent an important step in Serbia’s efforts to increase renewable generation and diversify a power system still heavily dependent on coal.
The project was financed primarily through international development support. KfW provided EUR 110 million in loans and a EUR 1.8 million grant, while the European Union contributed EUR 31 million through the Western Balkans Investment Framework. EPS provided an additional EUR 2.2 million.
The EU said its contribution had been fully disbursed by March, following the issuance of the certificate by the FIDIC project engineer. The funding structure underlines the strategic importance attached to Kostolac as one of Serbia’s major publicly supported renewable-energy projects.
The precise reasons behind the continuing shutdown remain unclear. Unconfirmed reports have linked the dispute to additional maintenance payments, but EPS, Siemens Gamesa and Serbia’s Energy Ministry have not publicly disclosed detailed information about the outstanding contractual issues.
Kostolac therefore remains a notable example of the gap that can emerge between technical completion and commercial operation. Although the turbines are installed, connected and capable of producing electricity, unresolved contractual and operational matters continue to prevent the project from entering regular service.
