With power surpluses projected to range between 48 GW and 115 GW due to changes in the technical minimum generation level of coal-based power stations, India could be staring at renewable energy curtailment in all 2030-31 scenarios even in the absence of transmission constraints.

A recent meeting of the National Committee on Transmission convened by the Central Electricity Authority (CEA) discussed the implications of coal-based generating stations operating at the technical minimum of 55% instead of 40%.

In February, a CEA committee had recommended operating thermal power plants at a minimum technical load of 40% since the grid was increasingly experiencing a pronounced “duck curve,” with surplus renewables during solar hours and steep evening ramp requirements. The Central Electricity Regulatory Commission had also suggested that thermal plants adopt two-shift operations to support grid stability.

According to load-generation balance studies of the Central Transmission Utility of India (CTUIL) as part of the rolling transmission plan for 2030-31, the grid could see surplus generation of 48 GW to 95 GW across seasonal and dispatch scenarios even if coal-based power stations operate at a technical minimum of 40%.

The surplus could increase to 68 GW and then to 115 GW if the technical minimum requirement of coal-based plants is kept at 55% instead of 40%. A higher technical minimum would reduce the system’s flexibility to scale down thermal generation during periods of high solar and wind output, increasing the need for renewable energy curtailment.

CTUIL considered a total demand of 446 GW under the Summer Solar Max scenario for June 2030. The estimate included 358 GW of base demand, 24 GW additional demand from green hydrogen and green ammonia, and 64 GW of energy storage system withdrawal, including battery charging and pumping at pumped storage projects during high solar hours.

On the power generation side, CTUIL considered a minimum thermal generation of 61 GW based on 40% of on-bar installed capacity. Hydro and nuclear generation were estimated at 53 GW, while solar and wind generation at 424 GW.

Even after accounting for additional demand from green hydrogen, green ammonia, battery energy storage systems, and pumped storage projects, CTUIL forecast an absolute generation surplus of 95 GW in the Summer Solar Max scenario. Similar studies for the monsoon scenario in August 2030 and the winter scenario in February 2031 showed surpluses of 55 GW and 48 GW, respectively.

According to CTUIL, these scenarios indicate that renewable energy curtailment would be required across seasons and dispatch scenarios even if there are no transmission constraints.

Expert member S R Narasimhan told the meeting that if the technical minimum for coal-based thermal plants is increased to 55%, the surplus would rise further by around 20 GW. He cautioned against artificially correcting the load-generation balance by reducing thermal generation to technically non-feasible levels in transmission planning studies.

Calling for consistency between transmission planning studies and the CEA’s Long-Term National Resource Adequacy Plan, he said the impact of reduced flexibility is already visible. In 2025-26, interstate transmission system (ISTS)-connected wind and solar generation had to be backed down through Tertiary Reserves Ancillary Services (TRAS) for 176 days, or nearly every second day. Around 2.7 billion units of energy were curtailed through this route, corresponding to an annual curtailment of 2.5%.

From May 1- 3 this year, nearly 25 GW of ISTS-connected renewable energy was curtailed through ‘TRAS down’ during a single 15-minute time block.