Located on the Subansiri River—a major tributary of the Brahmaputra—the Subansiri Lower Hydroelectric Project is situated at Gerukamukh, along the boundary between Arunachal Pradesh and Assam. Upon complete commissioning, the project will become India’s largest hydropower station by installed capacity, featuring eight 250 MW Francis turbines for a total capacity of 2,000 MW.
NHPC stated that, in a 90% dependable year, the plant is projected to generate approximately 7,421.59 million units of electricity annually.
The project comprises a 116-metre-high (from riverbed) concrete gravity dam with a crest length of 284 metres. Construction commenced more than twenty years ago but faced extended delays owing to technical complexities, environmental considerations, and community concerns. Major works resumed in 2019 following necessary regulatory approvals.
Since then, NHPC has achieved several key milestones, including the completion of pressure-shaft steel liners for all eight water-conductor systems earlier in 2025. The successful grid synchronisation of Unit-2 marks another significant step forward.
With this development, the Subansiri Lower project moves closer to full commercial operation, now targeted for mid-2026. Once all eight units are commissioned, the facility will substantially contribute to India's renewable energy capacity and support grid stability in the north-eastern region.
The milestone reflects continued progress in large-scale hydropower development and reinforces NHPC's role in expanding clean, indigenous power generation across the country.
