CTUIL Sets Two-Hour and Four-Hour BESS Norms, Outlines REGS Rules

The Central Transmission Utility of India Ltd. (CTUIL), has prescribed minimum discharge durations of two hours for eligible Right of First Refusal (RoFR) category Battery Energy Storage System (BESS) applications and four hours for non-RoFR applications and standalone BESS projects at renewable energy pooling stations and substations. The advisory also outlines requirements for installing commensurate Renewable Energy Generating Stations (REGS) for battery charging. 

The two-hour minimum applies to eligible connectivity grantees under Regulation 4.1, including entities eligible to apply under Regulation 5.11(b) of the Connectivity and General Network Access (GNA) Regulations. It covers specified applications submitted under Regulation 5.2 up to February 21, 2026, excluding those received for technical compliance, and applications under Regulation 5.11(a) submitted between September 9, 2025, and February 21, 2026. The provision also covers eligible entities whose Regulation 4.1 connectivity applications were under process as of September 9, 2025, subject to the specified regulatory conditions.

For RoFR applications under Regulation 5.2, the advisory provides three options concerning renewable energy capacity for BESS charging. Under Option A, applicants must apply for installation of commensurate co-located REGS under Regulation 5.2. They must ensure that the rated inverter capacity connected to the Inter-State Transmission System (ISTS) remains within the granted connectivity quantum at all times.

Under Option B, applicants proposing co-located REGS through a direct AC-side interconnection to supply power through the ISTS, in addition to charging the BESS, must also apply under Regulation 5.2. Option C covers charging the BESS using REGS associated with earlier connectivity or through the ISTS, for which a separate application for commensurate REGS is not applicable.

For eligible RoFR applications under Regulation 5.11(a), the minimum discharge duration is also two hours. Under Option A, applicants are not required to submit an application for installation of commensurate co-located REGS for BESS charging, in accordance with Annexure IV, Clause 1(l) of the GNA Regulations. However, the rated inverter capacity connected to the ISTS must remain within the granted connectivity quantum.

Applicants must inform the authorities of the quantum of commensurate co-located REGS before issuance of the final connectivity grant, if the capacity has not already been specified in the application. Where the final grant has already been issued, the applicant must communicate the details in writing for the necessary amendment to the grant letter. Under Option B, an application under Regulation 5.2 is required where the co-located REGS is intended to supply power through the ISTS in addition to charging the BESS. Option C is not applicable to this category.

For non-RoFR applications, the minimum BESS discharge duration is four hours. This covers applications under Regulation 5.11(a)(i) and specified applications under Regulation 5.11(a)(ii), including those received between September 9, 2025, and February 21, 2026, from entities not eligible under Regulation 5.11(b) or Annexure IV(4) of the GNA Regulations, as well as applications received on or after February 22, 2026.

For these applications, a separate application for installation of commensurate co-located REGS for BESS charging is not required, in line with Annexure IV, Clause 1(l) of the GNA Regulations. Applicants whose applications are under process must inform the authorities of the proposed REGS capacity during or after the Connectivity and Medium-Term Open Access System (CMETS) meeting, if the details have not already been specified. Fresh applicants must mention the corresponding capacity as REGS for BESS charging in the 'Installed capacity' field while submitting applications under Regulation 5.11(a).

Standalone BESS applications under Regulation 4.1 at renewable energy pooling stations or substations are also subject to a minimum four-hour discharge duration. These projects require an application under Regulation 5.2 for installation of commensurate co-located REGS.

The advisory states that installing commensurate co-located REGS for BESS charging is desirable for optimal utilisation of the ISTS grid. It specifies that the renewable energy generation capacity should be equivalent to the MWh capacity of the BESS being installed. The co-located REGS may be commissioned alongside the start date of the BESS entity's connectivity or within 36 months from the date of the in-principle connectivity grant or the firm start date of connectivity, whichever is later.

BESS entities will also be permitted to draw electricity from the ISTS grid for charging, subject to the availability of transmission margins.

The advisory provides a transition mechanism for certain pending applications proposing storage durations below the prescribed four-hour minimum. This applies to standalone BESS projects under Regulation 4.1 and non-RoFR BESS applications under Regulation 5.11(a) that were under process without an in-principle connectivity grant on the date of publication.

Such applicants will be given an opportunity to increase their energy storage capacity in MWh without changing their installed capacity in MW during discussions at the respective CMETS meetings. The revised capacity details will be incorporated into the intimation for grant of connectivity, subject to applicants submitting the requisite eligibility documents under Regulation 5.2(h) of the GNA Regulations.

The documents must be furnished within two months from the date of publication of the advisory or the CMETS meeting at which the application is agreed for grant, whichever is later. Applicants must also meet the corresponding land requirements, financial closure conditions, commissioning timelines and other applicable regulatory provisions associated with the enhanced energy storage capacity.