Itanagar, May 8: NHPC Limited has commissioned the fourth generating unit of the 2,000 MW Subansiri Lower Hydroelectric Project (SLHEP), taking the project’s total operational capacity to 1,000 MW.
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| Aerial view of the Subansiri Lower Hydroelectric Project located along the Assam-Arunachal Pradesh border, where NHPC Limited has commissioned the fourth 250 MW generating unit, taking the project’s operational capacity to 1,000 MW. (File Photo) |
According to the company, the 250 MW Unit 4 of the project, located along the Assam-Arunachal Pradesh border, commenced commercial operations at midnight on May 8. The project consists of eight generating units of 250 MW each.
With the latest development, four units of the mega hydropower project are now operational. Unit 2 was commissioned in December 2025, followed by Unit 3 in February 2026 and Unit 1 in March this year. NHPC said the remaining four units are expected to be commissioned in phases by the end of 2026.
The Subansiri Lower project, being developed on the Subansiri river, is expected to generate around 7,421 million units of electricity annually after full commissioning. NHPC said the project would help meet peak power demand, strengthen grid stability and support the integration of renewable energy into the national grid.
NHPC Chairman and Managing Director Bhupender Gupta described the commissioning as a major milestone for one of India’s largest hydroelectric projects. He thanked the Ministry of Power and the governments of Assam and Arunachal Pradesh for their support and appreciated the efforts of the project team led by Executive Director Rajendra Prasad.
The company stated that Unit 4 had successfully completed its trial run on May 1 before beginning commercial operations.
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The Subansiri Lower Hydroelectric Project has had a prolonged and controversial history since construction began in 2005 after forest clearance was granted in 2004. Work on the project remained suspended between December 2011 and October 2019 following widespread protests in Assam over safety concerns, seismic vulnerability and downstream ecological impact.
Construction later resumed after legal challenges before the National Green Tribunal were resolved and certain design modifications were introduced.
Originally scheduled for completion in 2012, the project has witnessed a sharp rise in cost, increasing from an estimated Rs 6,285 crore in 2002 to nearly Rs 27,000 crore.
NHPC said the project incorporates several environmental and safety measures, including sediment management systems, flood moderation provisions and year-round environmental flow releases to maintain downstream ecology. The company also stated that no habitation would be submerged by the project and that compensation and rehabilitation measures are being implemented in line with Arunachal Pradesh’s rehabilitation and resettlement policy.
According to NHPC, compensatory afforestation activities are also being carried out in Assam and Arunachal Pradesh through CAMPA funds, while riverbank protection works, flood forecasting systems and early warning mechanisms have been established downstream.
