Central Transmission Utility of India Limited (CTUIL) has issued an advisory introducing updated requirements for Battery Energy Storage Systems (BESS) and co-located Renewable Energy Generating Stations (REGS) used for charging. The guidelines specify minimum energy storage discharge durations, connectivity conditions, and commissioning timelines to improve the efficient utilisation of the Inter-State Transmission System (ISTS) grid.
Under the revised framework, connectivity applications are classified into different categories based on their eligibility and application timelines. Projects falling under the Right of First Refusal (RoFR) category will be subject to a minimum BESS discharge duration of two hours. This requirement applies to existing connectivity grantees and eligible applicants who submitted applications under Regulation 5.2 or Regulation 5.11(a) up to February 21, 2026.
Applicants under the RoFR category must also comply with the applicable conditions for co-located renewable energy generation and inverter capacity. Depending on the option selected, developers may be required to apply for co-located REGS under Regulation 5.2 or ensure that the total connected rated inverter capacity remains within their granted connectivity limits at all times. These provisions are intended to maintain compliance with approved transmission connectivity arrangements.
For applications outside the RoFR category, CTUIL has prescribed a minimum BESS discharge duration of four hours. The same requirement applies to standalone BESS projects located at renewable energy pooling stations. The higher storage duration is intended to support better utilisation of available transmission infrastructure and improve the operational efficiency of energy storage installations.
Although applying for co-located REGS may not be mandatory for every non-RoFR applicant under Clause 1(1) of Annexure IV of the General Network Access (GNA) Regulations, CTUIL has encouraged developers to install matching renewable energy generation capacity equivalent to the BESS energy storage rating in megawatt-hours (MWh). For standalone BESS projects at pooling stations, however, applications for co-located REGS under Regulation 5.2 remain mandatory. Developers must also ensure that inverter output stays within the permitted connectivity limits.
CTUIL has further advised that the capacity of co-located renewable energy generating stations used for charging should match the BESS storage capacity. These charging facilities must be commissioned either from the start date of BESS connectivity or within 36 months from the date of the in-principle grant or firm start date, whichever is later. Developers may also draw electricity from the national grid to charge their storage systems, subject to the availability of transmission margins.
The advisory also provides a transition mechanism for pending applications that do not currently meet the four-hour storage requirement. Applicants with under-process standalone BESS or non-RoFR projects may seek an increase in energy storage capacity in MWh without changing the overall installed power capacity in MW. Such requests can be raised during Connectivity and Medium-Term Open Access System (CMETS) meeting discussions.
Developers choosing to upgrade their projects must submit the required eligibility documents under Regulation 5.2(h) within two months of the advisory’s publication or the relevant approving CMETS meeting, whichever is later. The upgraded projects must also comply with applicable land requirements, financial conditions and scheduled commercial operation date (SCOD) regulations.
Through these measures, CTUIL aims to establish clearer storage requirements for different connectivity categories while supporting efficient transmission planning and the integration of renewable energy and battery storage projects into India’s power grid.
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