Building flexibility is central to accommodating increasing solar

India increasingly needs to move beyond simply adding renewable energy capacity to building a power system capable of absorbing high and variable renewable generation and that can only happen if sufficient flexibility is built.

Internationally, countries with higher renewable penetration have faced challenges in integrating an increasing share of renewable energy. Ember’s reports discuss country-specific experiences and outlines the policy and operational measures used to reduce renewable energy curtailment by building flexibility by adopting a combination of nine clean flexibility tools.

While a wide range of flexibility tools exists, this report focuses on those that are already emerging in the Indian context and can be readily scaled. These include:

• Supply: generating assets becoming flexible and easy to turn off or down when there is excess solar and wind.
• Store: storing excess renewable power for times of higher demand.
• Shift: shifting non-critical demand to periods of abundant renewable availability.

As of December 2025, India has around 226 GW of installed coal capacity, of which states own about 74.5 GW, central public sector companies (CPSU) such as NTPC own 76.9 GW, and the private sector owns the remaining.

Coal supplies the largest share of India’s electricity demand and in 2024, it accounted for 74.8% of total electricity generation. With the increasing share of renewable energy in the grid, the role of coal is shifting from baseload supply to providing flexibility to accommodate renewable generation. To operationalise this shift, the CERC, in the latest Indian electricity grid code (IEGC 2023), formalises the minimum thermal load, or minimum technical limit applicable to all grid-connected coal power plants, at 55%.

Although, at present, only a subset of generating stations participates in these balancing operations. During periods of sharp demand decline, it can become difficult to arrange sufficient downward reserves, constraining system flexibility. Extending operational control to additional resources would provide greater headroom for system manoeuvring and reduce the need to curtail solar generation.

Enabling the coal fleet to flex continuously would require:

• Aligning State Grid Codes with IEGC 2023: State Grid Codes should be aligned with the Central Electricity Authority’s Flexible Operation of Coal-based Thermal Power Generating Units Regulations, 2023 and the Indian Electricity Grid Code (IEGC), 2023, to ensure a consistent and enforceable framework for flexible operation across the country.
• Immediate compliance with the minimum technical limit of 55%: Generators should design or suitably retrofit all coal-based units to operate flexibly and comply with the MTL of 55%. A robust monitoring and reporting mechanism will ensure compliance, including regular disclosure of achieved minimum load levels and instances of non-compliance. Training personnel on standard operating procedures for achieving MTL is also crucial.

  Further, according to the phasing plan released by the Central Electricity Authority (CEA) time-to-time, coal-based generating units need to achieve a minimum technical limit of 40% on a sustained basis through technological interventions, in a phased manner, by December 2030.

• Piloting two-shift operation: Old and small-sized thermal generating units can be operated under two shifts. They can shut down during high-solar periods and operate during evening peak-demand periods on a pilot basis. However, assessing the technical and economic feasibility of such an operation is necessary.

Energy storage is already gaining momentum for different applications in India. At present, India has 7.2 GW of operational pumped hydro storage capacity and 0.5 GWh of battery energy storage (BESS) capacity. This capacity is likely to ramp up under the National Electricity Plan (NEP) 2032.

In a high variable renewable energy system, energy storage can absorb surplus renewable energy during periods of oversupply and shift it to periods of higher demand. Energy storage, especially BESS, can also provide ancillary and balancing services under CERC’s Ancillary Services Regulations, 2022 and be paid to charge in the emergency TRAS-Down market in future.

Energy storage filling the flexibility gap would require:

• Sustained momentum of energy storage deployment: Ensuring tendered stand-alone storage projects and renewable-plus-storage capacities are built out in a timely manner will help energy storage capacity additions. Operationalising the CEA’s advisory on co-locating energy storage systems with solar power projects is another way to maintain the momentum on storage capacity additions.
• Appropriate policy and regulatory frameworks: This would enable and compensate battery energy storage systems, as well as increase accessibility and transparency for providing reserves under secondary and tertiary and emergency ancillary services.
• Piloting energy storage with coal power plants: Installing energy storage tied to existing coal power stations could be explored, so that excess energy available during solar hours can be stored and later utilised during peak demand periods.

  NTPC has already issued a 1.7 GW battery tender across 11 coal plants, among the world’s largest. It includes 300 MW of four-hour systems (1,200 MWh) and 1,400 MW of two-hour systems (2,800 MWh), designed for twice-daily cycling over 12 years.

India is in the early stages of accessing demand-side flexibility by shifting consumption to hours of high renewable generation. A static time-of-day (ToD) tariff structure aligned with high solar generation hours has already been rolled out for most consumer categories, including commercial and industrial (C&I), residential and electric vehicle charging. However, despite C&I consumers being the largest contributors to electricity demand, their meaningful load shifting to solar hours will hinge on the adequacy of the tariff differential provided.

Additionally, the associated infrastructure required to operationalise ToD tariffs, especially the installation of smart consumer meters, needs to be accelerated at the state level. Out of the total sanctioned (approved for each distribution company under the Reforms-Based and Result-Linked scheme) smart consumer meters, only 19% are installed as of December 2025. The challenges behind this slow progress vary across states and range from regulatory gaps, delayed implementation, consumer awareness, and lack of transparency in the smart meter procurement processes.

Accessing demand-side flexibility will require:

• State-level deployment of smart meters to be accelerated by addressing regulatory gaps, ensuring timely implementation, increasing consumer awareness, and introducing greater transparency in procurement processes.
• Time-of-day tariffs to be designed and priced attractively to incentivise consumers to shift demand in line with system needs and available renewable generation.

No clean energy system can exist without flexibility. Enhancing coal fleet flexibility, scaling up energy storage, and enabling demand-side flexibility are central to integrating high shares of renewable energy. These measures are complementary and most effective when deployed in a coordinated manner across generation, storage and consumption. System-wide adoption of these measures, underpinned by aligned regulations, appropriate market signals, and timely implementation, will be essential for India’s transition from a capacity-centric to a flexible, renewables-ready power system.