The Tamil Nadu Electricity Regulatory Commission (TNERC) has issued a comprehensive framework for renewable energy transactions through the Tamil Nadu Electricity Regulatory Commission’s Terms and Conditions for Green Energy Open Access (GEOA) Regulations, 2025.

The notification outlines the terms for non-discriminatory access to green power using intra-state transmission and distribution networks.

Objective and Scope

The regulations are designed to facilitate the purchase, sale, and banking of renewable energy by consumers, generators, and traders. Open access is permitted for electricity generated from solar, wind, hybrid, small hydro, biomass, and waste-to-energy projects that utilize non-fossil fuels.

The scope extends to intra-state transmission and distribution systems, including their incidental use for inter-state transactions. In addition to the eligibility and procedural requirements, the regulations clearly define how ransmission charges, wheeling charges, cross-subsidy surcharges, and banking charges will be determined and applied.

Nodal Agencies for Open Access

The regulations establish a dual nodal agency structure. All applications must be submitted through the Central Nodal Agency portal, which will forward intra-state applications to the State Nodal Agency (SNA). To avoid administrative delays, applicants can also file directly with the SNA until national-level procedures are harmonized.

The Tamil Nadu state load dispatch center is designated as the SNA for short-term open access transactions, while the state transmission utility will handle medium- and long-term applications.

The regulations mandate that no open access will be permitted without the consent of the distribution licensee. This ensures that load obligations and consumer rights of distribution licensees are not compromised.

The SNA is also tasked with maintaining transparency by publishing GEOA information on its portal, including application status, capacity availability, and system constraints.

Criteria and Eligibility

Long-term access, with tenures ranging from 12 to 25 years, will be approved based on state transmission planning and distribution codes.

Medium-term access, lasting from over three months to three years, and short-term access of up to one month at a time, will be allowed depending on spare margins in the grid. Margins may arise from inherent design capacity, variations in actual power flow, or capacity created for future demand growth.

Long-term access

Eligibility extends to extra-high tension and high-tension consumers with a minimum contracted demand of 63 kVA. Renewable energy generating companies, traders, and distribution licensees are also eligible to apply. Captive generating plants are given statutory rights under Section 9 of the Electricity Act, and these rules reaffirm that entitlement.

However, all applicants must ensure compliance with technical standards, including the installation of interface meters with communication systems as per the Central Electricity Authority (CEA) regulations.

Treatment of Existing Entities

Consumers and generators already availing of renewable open access under existing agreements are allowed to continue until their contracts expire. They must continue to pay the charges agreed in those contracts. Once the term expires, or if additional renewable capacity is sought, such cases will fall under the new regulations.

For example, an existing industrial consumer sourcing 5 MW under an earlier framework may continue at the contracted terms; however, if it seeks to expand its procurement by another 3 MW, the new capacity will be governed by the 2025 regulations.

Priority Allotment

Distribution licensees are given the highest priority to ensure the fulfillment of their universal service obligations. GEOA customers rank above the normal open access customers, ensuring that renewable energy transactions are encouraged.

Within the GEOA category, priority is assigned to long-term customers first, followed by medium-term customers, and then short-term customers.

Where capacity is limited, applications are processed on a first-come, first-served basis. This priority mechanism aims to strike a balance between system reliability and the promotion of renewable energy.

Categorization of Access

Green Energy Open Access is categorized into three time frames: long-term (12–25 years), medium-term (3 months–3 years), and short-term (up to 1 month).

Short-term approvals require fresh applications for each extension, and each application will be treated independently for priority.

This classification ensures system planners can allocate long-term commitments with certainty while retaining flexibility for short-term and seasonal renewable energy requirements.

Energy Accounting and Billing

Energy accounting is conducted on a 15-minute block basis. The granularity ensures accurate measurement of power injection and consumption, preventing manipulation of surplus or deficit positions.

Surplus energy after set-off in a block is treated as banked energy, while excess consumption is billed at the consumer’s applicable tariff. Banking and withdrawal are permitted throughout the billing cycle, with separate provisions for adjustment during normal, peak, and off-peak hours.

For deviation charges, solar, wind, and hybrid generators fall under TNERC’s 2024 forecasting and deviation settlement regulations, while the 2019 deviation settlement framework governs other renewable sources. Hydropower and pumped storage stations remain exempt.

This distinction is important because variable renewable sources, such as wind and solar, require stricter deviation management to maintain grid stability.

Banking Facilities and Charges

Banking is permitted for intra-state GEOA transactions. Surplus renewable energy can be banked with the distribution licensee, and withdrawals are permitted within the same billing cycle. Charges are levied in kind at 8% of the banked energy.

Unlike earlier provisions, the new rules disallow the carry-forward of banked energy beyond a month, except for wind projects commissioned on or before March 31, 2018, which retain a 12-month facility with a 14% charge.

Unutilized energy at the end of the banking period must be sold to the distribution licensee. The purchase rate is set at 75% of the applicable renewable energy tariff or discovered bid tariff.

For captive projects under the REC arrangement, unutilized energy will be paid at 75% of either the pooled cost of power purchase for the year or the preferential tariff determined by TNERC, whichever is lower.

If no preferential tariff exists, 75% of the lowest bid tariff discovered by SECI or Tamil Nadu Generation and Distribution Corporation will apply.

Applicable Charges

GEOA customers are liable for all relevant charges, including transmission and wheeling charges, cross-subsidy surcharge, additional surcharge, banking charges, standby charges, reactive energy charges, and other fees such as SLDC scheduling charges and deviation settlement costs.

The Commission has clarified that consumers sourcing power through interstate transactions or power exchanges in GEOA will not be eligible for concessional charges on the intrastate network. This provision aims to prevent cross-subsidization of interstate trade at the cost of state network users.

Curtailment Priority

In situations where curtailment is necessary due to grid constraints, the regulations provide a structured order of priority. Short-term non-GEOA customers will be curtailed first, followed by short-term GEOA customers, then medium-term customers, and lastly long-term customers.

Within each category, GEOA customers are curtailed on a pro-rata basis. Distribution licensees are curtailed only as a last resort, ensuring their ability to meet consumer obligations.

Metering and Communication

All GEOA generators must install main and check meters at the generator and consumer ends. These must comply with CEA’s installation and operation standards. The interconnection point is defined as the nearest transmission or distribution substation.

Generators of 1 MW and above must provide real-time communication to the SLDC for energy accounting and grid management purposes. Failure to provide communication facilities within 30–45 days after notice may lead to partial or full exclusion of the generator’s output from dispatch and deviation settlement.

Detailed Procedure

The SLDC must publish a detailed procedure within 90 days of notification, and TNERC will approve it within 30 days thereafter. The procedure will cover application formats, eligibility checks, processing timelines, billing, payment security mechanisms, handling of defaults, and treatment of underutilized capacity.

It will also specify communication requirements, energy accounting formats, and day-ahead scheduling protocols. The procedure is expected to align with the guidelines issued by Grid Controller of India Limited in compliance with the Ministry of Power’s 2022 rules.

Recently, TNERC permitted the Tamil Nadu Transmission Corporation to lease portions of its substation land to private developers to install battery energy storage systems at a nominal charge of ₹1 (~$0.0113)/project/annum for 15 years.

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