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Grid Constraints Curtail 2.3 TWh of Solar Power in India in 2025: Ember Report

India’s rapid expansion of solar power capacity is increasingly running ahead of the electricity system’s ability to integrate clean energy, resulting in the curtailment of 2.3 terawatt-hours (TWh) of solar generation in 2025, according to a new report by energy think tank Ember.

The curtailed output represents enough electricity to power hundreds of thousands of homes and led to 2.11 million tonnes of unrealised carbon dioxide abatement, highlighting how grid inflexibility—rather than insufficient demand—is emerging as a key bottleneck in India’s clean energy transition.

India added a record 38 GW of solar capacity in 2025, but the power system struggled to absorb the additional generation, particularly during midday hours when electricity demand remained weak and coal-fired power plants were unable to ramp down quickly, the report said.

“Curtailment in 2025 was not caused by excess solar capacity, but by insufficient flexibility across the power system,” Ember noted.

Demand mismatch drives curtailment

The report pointed to a growing mismatch between daytime solar generation and evening peak demand. In October 2025, average midday electricity demand declined by 14 GW year-on-year to 185 GW, a drop that was twice as large as the reduction seen during evening hours.

To maintain grid stability and ensure availability of power later in the day, system operators were compelled to keep coal-based plants running even as solar generation peaked. This led to renewable energy being curtailed through Tertiary Reserve Ancillary Services, an emergency grid-balancing mechanism.

Due to their operational flexibility, renewable generators are often the first to be instructed to reduce output. Citing Grid-India’s daily Variable Renewable Energy (VRE) reports, Ember said that approximately 45 GWh of interstate transmission system (ISTS)-connected solar power was curtailed on 25 May 2025, rising to about 93.3 GWh on 12 October 2025.

Between May and December 2025, emergency curtailment accounted for nearly 18% of average monthly solar generation, the report added.

Economic and environmental impact

While renewable generators were compensated an estimated Rs5,750 crore to Rs6,900 crore, Ember cautioned that curtailment represents a wider economic and environmental loss.

“Every unit of curtailed solar is a missed opportunity to displace fossil fuel generation,” the report said, underlining the need for greater grid flexibility, faster deployment of energy storage, and improved demand-side management to fully utilise India’s rapidly expanding solar capacity.