Bulgaria has launched a EUR 350 million tender to build the Yadenitsa dam, a major expansion of the Chaira pumped storage hydropower plant, the largest facility of its kind in the Balkans.
The project will more than triple the water volume available to Chaira, allowing the plant to run for longer cycles and making better use of its existing 864 MW power generation capacity.
Bulgaria’s state-owned National Electricity Co. (NEK) has launched the tender for the Yadenitsa project, with bids due by 4 November 2026.
The investment was initially estimated at EUR 250 million but has now increased to EUR 350 million excluding VAT. The project is expected to receive financing from the Bulgarian state budget and European Union funds. The selected contractor will have 60 months to complete the works.
The project will connect the existing Chaira reservoir with the future Yadenitsa dam through a tunnel of more than six kilometres. This will increase the water volume available to the pumped storage plant from 4.2 million cubic metres to 13.4 million cubic metres.
The additional volume will give Chaira much longer operating cycles and improve its overall efficiency. The long-term aim is for the plant to operate around the clock.
Chaira has 784 MW of pumping capacity and 864 MW of power generation capacity and forms part of Bulgaria’s Belmeken-Sestrimo-Chaira hydropower complex. The Yadenitsa project is designed to expand what the existing facility can do rather than build an entirely new generation asset. With more water available, Chaira will be able to store and release electricity over longer periods and respond more effectively to changes in the power system.
The project has also been included in the European Union’s Projects of Common Interest (PCI) list.
Yadenitsa is part of a wider push to increase energy storage in Bulgaria. The country has identified ten potential sites for additional pumped storage hydropower plants, including Dospat, Batak and Chaira 2. At the same time, battery energy storage is expanding rapidly, with Bulgaria becoming one of Europe’s fastest-growing battery storage markets relative to the size of its economy and population. NEK is also continuing work on Chaira itself. The plant was shut down in 2022, but two units have since been restarted and a third is undergoing repairs.
Yadenitsa is significant because it builds on infrastructure Bulgaria already has. Instead of treating storage as a single technology, Bulgaria is developing a broader mix of pumped hydropower, batteries and upgraded existing assets. Yadenitsa would give one of the country’s largest power facilities substantially more room to store and deliver electricity, while the wider pipeline creates demand for civil works, tunnelling, electromechanical equipment, automation and grid infrastructure.
For the Balkan energy market, the project is a clear example of how large-scale storage is becoming part of the region’s core power infrastructure,، not simply an addition to renewable projects.
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