A report from energy think tank Ember shows that India’s system operator had to regularly limit solar power generation as an emergency measure to maintain the safety of the electricity grid, as other sources were already reaching maximum capacity.
India had to curtail 2.3 TWh of solar energy between the end of May and December 2025, including 0.9 TWh in October alone, according to a new report from energy think tank Ember.
The report states that a combination of incorrect forecasts, low daytime demand due to unusually mild temperatures and increasing solar power generation will have led to periods of daytime oversupply by 2025.
It adds that the inability to flex the coal fleet beyond technical limits limited the system’s ability to provide sufficient headroom, making solar curtailment necessary to maintain grid security.
“Weaker-than-predicted daytime demand coincided with the continued expansion of solar energy, resulting in periods when cumulative supply exceeded demand,” the report explains. “This was due to the need to keep sufficient coal capacity online to meet evening demand, with the mismatch raising concerns about the security of the electricity grid.”
Ember says the extent of the avoided curtailment in the future will depend on how accurately demand is forecast, how decisively India resolves transmission bottlenecks and how quickly it scales up its flexibility assets.
“A massive 38 GW of solar capacity was added in 2025. Yet curtailment of renewable energy emerged as a major theme of the year, driven by transmission restrictions and grid security concerns through emergency measures. In many ways, such curtailment undermines the very purpose of building this capacity,” said the report’s author, Ruchita Shah, energy analyst at Ember.
“While the 2025 grid security curtailment may not in itself be a major concern, as it was largely driven by lower-than-expected demand, it served as a real stress test for a solar-heavy future. It highlighted a fundamental reality: clean energy cannot be efficiently scaled without flexibility,” she added.
Ember’s report adds that transmission restrictions are the biggest driver of national solar curtailment, and pose the greatest risk to new projects as they are not guaranteed to be financially compensated.
The think tank estimates that affected solar generators have received an estimated INR 5,750 million – INR 6,900 million ($63 million – $76 million) in compensation through Tertiary Reserve Ancillary Service (TRAS) emergency mechanisms.
There is also an environmental price to pay, the report points out, as limited solar energy could have avoided around 2.1 million tonnes of CO2 emissions if coal production had been displaced, roughly equivalent to the annual emissions of 0.4 million households in India.
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