India needs 10 GWh battery storage to curb renewable curtailment: Ember

Energy think tank Ember says battery storage can absorb excess solar generation, reduce renewable-energy curtailment and help coal plants operate within technical limits

India requires about 10 gigawatt-hours (GWh) of battery energy storage systems (BESS) to prevent renewable-energy curtailment at times when coal-based thermal power plants cannot ramp down below their minimum technical load (MTL), according to an analysis by energy think tank Ember.

 

The report said keeping coal plants above their MTL forced the curtailment of around 2.1 terawatt-hours (TWh) of renewable generation in FY26, equivalent to 1.3 per cent of total renewable generation.

 

As solar power generation floods the grid during the daytime, many coal-based power plants are required to operate at or even below their MTL of around 55 per cent, the level at which they can safely operate. This leads grid operators to curtail clean electricity to keep thermal power plants online for the increase in demand at night.

 

“In 2026, around 10 GWh of storage, charging during the midday solar window, would have been enough to absorb that surplus, keep coal above its safe operating floor and avoid the curtailment altogether,” the report said.

 

Currently, coal provides almost all of the grid’s flexibility, including ancillary reserves. The report said that on March 6, 2026, solar and wind reached 41 per cent of the generation mix at midday, pushing coal down by around 49 GW in six hours before it had to climb back by 51 GW in the evening as solar generation declined.

 

Peak-hour curtailment had returned to 4 per cent of solar and wind generation by April 2026, comparable to the most constrained months of late 2025, despite April falling outside the worst seasonal window, the report noted. It further added that solar and wind energy curtailment due to the emergency Tertiary Reserve Ancillary Service (TRAS) down mechanism exceeded 3,600 GWh by early June 2026, from zero in mid-2025.

 

Citing the example of the 3.37 GWh Khavda project in Gujarat, the world’s largest outside China, commissioned within 10 months, the report said BESS can be deployed quickly. It claimed that site-ready projects can be built within five to seven months.

 

The report recommended that grid charging during solar-surplus hours be permitted by default, with withdrawal limits applied only where non-solar-hour use creates genuine network risk.