State-owned NHPC Limited (NHPC) announced on 3 December 2025 that the 250MW Unit-2 of the Subansiri Lower Hydroelectric Project (SLHEP) has been successfully test-synchronised with India’s national grid.
In its regulatory filing, NHPC said the synchroniszation occurred on the evening of 02 December 2025, and that commercial operation (CoD) of Unit-2 is expected by end of December 2025.
The Subansiri Lower project, built on the Subansiri River, a tributary of the Brahmaputra, straddles the border between Arunachal Pradesh and Assam, at Gerukamukh.
Once fully commissioned, it will be India’s largest hydroelectric power station by installed capacity, with eight Francis-type turbines of 250MW each, delivering a total of 2000MW.
According to NHPC, in a 90 % dependable year the project is estimated to generate around 7,421.59 million units (MU) of electricity.
Construction of the dam – a concrete gravity structure 116m high from the riverbed and 284m long – began over two decades ago. The project experienced long delays due to technical, environmental and social challenges, including landslides and opposition from local groups.
Work resumed in 2019 after clearance from environmental authorities, and NHPC has since marked a series of construction milestones, including the installation of pressure-shaft liners across all eight water-conductor lanes earlier this year.
With Unit-2 now grid-synchronised, the project is edging closer to full commercial commissioning, which is expected by mid-2026.
