India Lost 2.3 TWh of Solar Generation Due to Curtailment: Ember

While 2025 marked a surge in solar capacity additions in India, it also regularly saw curtailment of solar power as an emergency measure to ensure grid stability. A new report by energy think tank Ember finds that India had to curtail 2.3 terawatt hours (TWh) of solar generation between late May, when reporting started and December 2025, for which compensation between INR 5,750 million - INR 6,900 million (~USD 63 million - USD 76 million) had to be paid. The total recorded curtailment is equivalent to ~18% of the average monthly solar generation of ~13 TWh.

The curtailment occurred because, under frequently occurring operational conditions, the National Load Dispatch Centre could not turn down other generation sources far enough to accommodate midday solar. These conditions occurred, for example, when demand was lower than forecast, a common occurrence in 2025 due to exceptionally mild temperatures. Demand fell in October 2025, with the midday fall twice that in the evening. In these cases, even after ramping down the coal fleet to its minimum technical limits, the system operator had to curtail solar generation to ensure the grid remained stable.

Curtailment Flagged

“A massive 38 GW of solar capacity was added in 2025. Yet, curtailment of renewable energy emerged as a key theme of the year, driven by transmission constraints and grid security concerns through emergency measures. In many ways, such curtailment defeats the very purpose of building this capacity,” says the report’s author Ruchita Shah, Energy Analyst at Ember.   

“While grid security-related curtailment in 2025 may not be a major concern in isolation, as it was largely triggered by lower-than-expected demand, it served as a real-world stress test for a high-solar future. It highlighted a fundamental reality: clean energy cannot scale efficiently without flexibility,” she added.

Reasons Behind Curtailment 

While the report focuses on the reasons behind the emergency curtailment of solar, it notes that transmission constraints are the largest cause of solar curtailment nationally, and represent the largest risk to new projects as they are not guaranteed to be compensated financially. 

With regard to emergency curtailment, Ember estimates that affected solar generators received an estimated INR 5,750 million - INR 6,900 million (~USD 63 million - USD 76 million) in compensation through emergency Tertiary Reserve Ancillary Service (TRAS) mechanisms. The report highlights that in addition to the economic cost, there is also an environmental price to pay. The curtailed solar could have avoided around 2.1 million tonnes of CO2 emissions had it displaced coal generation, roughly equivalent to annual emissions by 0.4 million households in India.

The report argues that 2025 is an indicator of the power system’s requirements for a high-renewables future, and shows that Indian flexibility improvement must keep pace with solar capacity growth. It identifies that India is already taking steps in this direction, and recommends a three level strategy, implemented in the near to mid term to increase flexibility. First, ensuring that other generating assets are capable of turning up or down when there is high renewable generation. Second, building more storage assets to store excess renewable energy for times of higher demand. Finally, shifting non-critical demand to periods of high renewable availability as another key step to prepare for the future.