New Delhi, Jan. 28 -- While 2025 saw 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 Ember, an energy think tank, flagged on Tuesday. The report by Ember found 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 had to be paid to generators. The total recorded curtailment is equivalent to ~18% of the average monthly solar generation of ~13 TWh, the analysis said. The curtailment occurred because the National Load Dispatch Centre could not turn down other generation sources far enough to accommodate midday solar, the analysis said. These conditions can occur when demand is lower than forecast. In 2025, this may have happened due to exceptionally mild temperatures. The system operator had to curtail solar generation to ensure the grid remained stable, the analysis said, stressing the need for grid security to accommodate growing solar capacity in India. HT had sought comments from the power ministry on Ember's findings. "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 verypurpose of building this capacity," said 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. 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 400,000 households in India, the report has projected. A combination of forecast error, low daytime demand and rising solar generation led to periods of daytime oversupply in 2025 according to the analysis which is based on Grid-India's daily Variable Renewable Energy (VRE) reports for the period May-December 2025....