India is close to starting a mega hydropower project that has been in the works for 20 years, a key step in the country’s energy transition.

State-run hydropower company NHPC will start trial runs in July for the Subansiri Lower project that runs through Assam and Arunchal Pradesh in the country’s north-east. The first unit is expected to be commissioned in December, according to finance director Rajendra Prasad Goyal. By the end of 2024, all eight units will be commissioned. 

Hydropower, with its ability to quickly respond to fluctuations in electricity demand, is seen crucial for balancing the grid as intermittent generation of solar and wind power rises. However the 2-gw project, started in 2003, was delayed by protests and litigation, driven by concerns over environment damage.

The cost of the project jumped to Rs 21,250 crore ($2.6 billion), more than three times the original estimate. The National Green Tribunal allowed the work to resume in 2019 after eight years of suspension. Opposition to dams has limited the country to tapping barely a third of its hydropower potential of 145 gw. 

“We need to get nearly 40 approvals from different departments before we start building a hydropower project. All the scrutiny should be done at this stage,” Mr Goyal has said. “Any stoppage after the construction has begun is problematic.”