Bulgaria’s pumped-storage hydropower plant Chaira has reached a significant milestone in its ongoing modernization. In mid-May, Unit 2 officially received final regulatory approval, marking the successful completion of its restoration. With this clearance, the National Electricity Company (NEK) is now authorized to fully integrate the unit into the national electricity network, finalizing the last stage of its rehabilitation.
Unit 2 has already been contributing to Bulgaria’s electricity supply since December, providing essential support during periods of peak demand. Often referred to as the largest energy storage system in the Balkans, HPP Chaira continues to play a vital role in managing peak loads and maintaining grid stability.
While Unit 2 is now fully operational, NEK is also advancing repair efforts on Units 1 and 3. Unit 1 is slated for complete replacement over the long term, but in the interim, Toshiba Corporation is conducting key restoration work to restore its functionality. Simultaneously, the refurbishment of Unit 3 is progressing under the guidance of the Austrian Voith-ABB consortium, which is implementing a customized technical solution similar to that used for Unit 2.
In a broader modernization initiative, NEK has launched a formal procedure to replace both Units 1 and 4 entirely. Five leading hydropower companies have submitted bids for the project, which are currently under review. Once the evaluation phase is complete, the project will advance to the second stage of the tender process.
These upgrades are designed to secure HPP Chaira’s long-term operational capacity and strengthen its role as a cornerstone of Bulgaria’s energy infrastructure, enhancing the reliability and sustainability of the national electricity system.
