India Needs 10 GWh Battery Storage to Prevent Rising Renewable Energy Wastage, Says Report

India requires around 10 GWh of battery energy storage capacity immediately to prevent the curtailment of renewable energy caused by operational constraints in the country's coal-fired power fleet, according to a new analysis by energy think tank Ember.

The report highlights that rapid growth in solar generation is creating surplus electricity during midday hours, while coal-based power plants are unable to reduce output below their minimum technical load (MTL) requirements. As a result, grid operators are increasingly forced to curtail renewable energy to maintain grid stability and keep coal plants available for evening demand peaks and reserve requirements.

According to Ember, around 2.1 TWh of renewable electricity generation was curtailed during FY 2025-26 because coal plants had to remain above their technical minimum operating levels. The analysis estimates that approximately 10 GWh of battery storage, charged during periods of excess solar generation, would have been sufficient to absorb this surplus energy and eliminate the need for such curtailment.

"Solar and wind curtailment is becoming a visible part of India's real-time grid balancing, and the volumes are already noticeable and rising," said Neshwin Rodrigues, Senior Energy Analyst at Ember and author of the report. He warned that inadequate flexibility resources, particularly battery storage, could become a major constraint on the next phase of renewable energy expansion.

The report notes that coal continues to provide most of the grid's flexibility and ancillary reserves. As solar penetration increases, coal plants are being forced into daily cycles of steep ramp-downs during the day and rapid ramp-ups in the evening. On March 6, 2026, solar and wind accounted for 41 percent of the generation mix at midday, causing coal generation to fall by around 49 GW within six hours before rising by 51 GW later in the evening as solar output declined.

Ember stated that once coal plants reach their MTL, typically around 55 percent of rated capacity, they can no longer provide additional downward flexibility. By April 2026, coal generation breached this threshold in more than half of all midday dispatch intervals, forcing renewable curtailment to meet 37 percent of down-regulation requirements during the month.

The report describes the issue as a structural constraint, noting that renewable energy is increasingly being curtailed simply to maintain coal plant operability, even before accounting for reserve requirements or transmission bottlenecks.

India added nearly 24 GW of solar capacity between October 2025 and April 2026, taking total installed solar capacity to around 154 GW. However, curtailment levels have also increased, with solar and wind curtailment linked to the emergency Tertiary Reserve Ancillary Service (TRAS) down mechanism exceeding 3,600 GWh by early June 2026. More than 1,400 GWh of additional curtailment occurred in just two months after March 2026, while daily curtailment volumes surpassed 120 GWh on both May 1 and May 3, 2026.

Ember said that accelerated deployment of battery energy storage systems will be critical to improving grid flexibility, reducing renewable energy wastage, and supporting India's clean energy transition.