Second unit of Subansiri Lower hydro project to start commercial ops from Dec 23

New Delhi, Dec 21: State-owned NHPC will begin commercial operations of the second unit of the 2,000 MW Subansiri Lower Hydroelectric Project from Tuesday.

In an exchange filing, NHPC said it had declared the commercial operation of Unit-2, with a capacity of 250 MW, from 00:00 hours on December 23, 2025.

The 8×250 MW run-of-the-river project is located at Gerukamukh near North Lakhimpur, along the border of Arunachal Pradesh and Assam, and involves water storage on the Subansiri.

Developed at an estimated cost of around Rs 27,000 crore under the Ministry of Power, once fully commissioned, the plant will have eight Francis-type turbines and an installed capacity of 2,000 MW, making it the largest hydroelectric power station in the country.

NHPC Director (Projects) Sanjay Kumar Singh was present at the project site to oversee the commencement of commercial operations.

During his visit, Singh inspected key infrastructure components, including the main dam, diversion tunnel and spillway structures, and held interactions with contractors and other stakeholders to review pending works.

The 250 MW Unit-1 was successfully test-synchronised with India’s national grid on December 3, indicating operational readiness.

According to NHPC, the project is expected to generate about 7,421.59 million units of electricity in a 90% dependable year.

The final four units are scheduled for sequential connection during 2026–27, further enhancing energy supply and supporting national infrastructure.

Construction of the concrete gravity dam, 116 metres high from the riverbed and 284 metres long, began over two decades ago.

The project witnessed prolonged delays due to technical, environmental and social challenges. Construction came to a halt for eight gruelling years between 2011 and 2019, stalled by Assam’s protests and court battles over fears of dam safety and downstream ecological fallout.

But with fortified mitigation plans in place, the project construction roared back to life in October 2019, transforming scepticism into steady progress.

NHPC officials said the Subansiri project is designed as a run-of-the-river scheme, harnessing the river’s natural flow while keeping construction scale and environmental impact lower than conventional large-reservoir projects.

They added that the approach aligns with India’s broader push for scalable and ecologically sensitive hydropower development.

With inputs from PTI