Bulgaria has reached another milestone in the restoration of the Chaira pumped-storage hydropower plant, with Unit 3 officially cleared for commercial operation. The National Electricity Company (NEK) said the unit completed all regulatory and technical approval procedures required for return to service.
NEK announced that the unit received its final operating permit after an inspection by the state commission. The approval indicates that rehabilitation works satisfy technical, construction, and legal requirements. Inspectors also confirmed that the refurbishment was carried out in line with approved engineering plans and applicable standards.
Chaira Unit 3 returns to regular service
The certification completes the recovery process for Unit 3 and supports the gradual restoration of HPP Chaira toward full functionality. NEK described the clearance as enabling the facility to return to regular service following completion of rehabilitation activities. The state commission’s inspection outcome was cited as the basis for the operating permit.
The HPP Chaira site is positioned to provide balancing and flexibility services within Bulgaria’s electricity system and the wider Balkan power market. It is described as the largest pumped-storage hydropower plant in the region. The plant had been largely offline for several years after unsuccessful repair works led to shutdown of its generating units.
Ongoing restoration for Units 1 and 4
NEK continues restoration work across remaining units at Chaira. Rehabilitation for Unit 1 is being performed by Japan’s Toshiba Corporation under an agreed schedule, with completion expected in 2028. Preparations are also underway for recovery of Unit 4.
The utility is advancing a broader program aimed at fully restoring this energy storage and generation asset. NEK said the return of additional capacity at Chaira is expected to strengthen Bulgaria’s ability to balance renewable energy production. It also cited improvements to grid reliability and overall energy security across the region.
