New Delhi: State-owned NHPC Limited has successfully test-synchronised the 250 MW Unit-2 of the 2,000 MW Subansiri Lower Hydroelectric Project (SLHEP) with the national grid, the company informed stock exchanges on Wednesday. NHPC confirmed that the Commercial Operation Date (CoD) for Unit-2 is expected in December 2025.
About the Subansiri Lower Hydroelectric Project
The Subansiri Lower Hydroelectric Project, located on the Subansiri River at Gerukamukh on the Assam–Arunachal Pradesh border, is a run-of-river scheme with water storage, designed to house eight units of 250 MW each, totaling 2,000 MW. Once fully commissioned, it will become India’s largest hydropower project by installed capacity. The project is expected to generate around 7,400–7,500 million units of electricity annually, supporting grid stability and meeting power demand in the North East and across the national grid.
Construction of the project has faced significant delays due to environmental concerns, local protests, and monsoon-related damages, pushing the commissioning timeline far beyond the original December 2012 schedule. Project costs have also escalated from an initial estimate of Rs 6,285 crore to approximately Rs 26,075 crore. NHPC stated that recent minor monsoon damages pose no risk to the dam structure, although such incidents have contributed to schedule slippages.
Commissioning Progress and Timelines
Unit-1 of Subansiri Lower entered wet commissioning in October 2025, with NHPC confirming one 250 MW unit had already been test-run. Unit-2’s successful test synchronisation now allows a combined 500 MW to be progressively brought online as procedures are completed.
Earlier plans aimed to commission three units of 250 MW each starting June 2025, subject to National Dam Safety Authority clearance, with the remaining five units expected in phases by May 2026. Latest updates suggest that the full 2,000 MW commissioning may be achieved around May 2026, reflecting site challenges and revised schedules.
NHPC has indicated that the regulated equity for Subansiri Lower will be fully factored in from FY 2026–27, which is expected to significantly enhance earnings. Full commissioning of the project is projected to add several thousand crore rupees to NHPC’s annual revenue while supporting India’s clean-energy goals and providing flexible peaking power from the North Eastern region.
About NHPC
NHPC Limited, a state-owned hydropower utility, is India’s leading central public sector company in hydroelectric power generation. Established in 1975, NHPC develops, operates, and maintains large and small hydroelectric projects across the country, contributing to India’s clean energy transition and grid stability.
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