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Regulatory Approvals
Inter-state transmission system (ISTS) open access approvals through CERC — giving industrial consumers access to the national power market and competitively priced generators across India.
Overview
ISTS open access allows large consumers to source power from generators in other states via the inter-state transmission network operated by Power Grid Corporation. Unlike intra-state open access (regulated by APERC/TGERC), ISTS is governed by CERC and managed through the Central Transmission Utility (CTUIL, a Power Grid subsidiary notified as CTU in 2021). The process involves connectivity applications through the National Single Window System (NSWS), CERC approval, and coordination with the relevant State Load Despatch Centres and RLDCs. A critical change to understand: the 100% ISTS charge waiver for renewable energy projects ended on 30 June 2025. Projects commissioned from July 2025 onward receive a declining waiver — highest for earlier commissioning dates and stepping down toward 2028, with no waiver for projects commissioned after 30 June 2028. ISTS strategy must now be evaluated carefully against this phased charge reduction, and the exact waiver percentage for a given commissioning date should be confirmed against the current CERC order before structuring.
Why Daakshyaani
The 100% ISTS charge waiver for renewables ended 30 June 2025. Projects commissioned from July 2025 receive a declining waiver that steps down as the commissioning date approaches June 2028, after which no waiver applies. Structuring an ISTS arrangement without confirming the current waiver percentage against the latest CERC order leads to unexpected charge exposure. We evaluate the waiver position for every new project before structuring.
As ISTS waiver phases out, intra-state (SSTS) open access is increasingly competitive for AP/TG consumers. ISTS makes sense for very large loads buying from distant low-cost generators; intra-state suits most industrial consumers within the state. We model both options against the specific load profile before recommending.
The Central Transmission Utility of India Limited (CTUIL) is the dedicated CTU entity under Power Grid, notified in 2021. Connectivity applications now go through the National Single Window System (NSWS) in monthly batches. We work under the current CTUIL/NSWS framework — not the pre-CTUIL process.
ISTS approval requires coordination across CERC (regulatory), NLDC (national scheduling), SRLDC/SR-RLDC (regional), and state DISCOMs (wheeling at both ends). We manage this entire multi-agency workflow so clients interface with a single point of contact — not five different regulators.
Battery energy storage systems co-located with renewable projects at the same ISTS-connected substation qualify for a 12-year full ISTS charge waiver. For eligible projects, this is a structuring opportunity worth capturing before the BESS waiver window closes.
ISTS DSM charges for schedule deviations are governed by CERC — and inter-state deviations carry higher financial exposure than intra-state. We monitor scheduled vs. actual drawl across state boundaries and advise on real-time schedule corrections to minimise DSM costs.
Blog
Intra-state (or "state") open access lets a consumer buy power from a generator within the same state, coordinated through the SLDC alone. ISTS open access extends that to generators in other states, using the national inter-state transmission network — which brings in CERC as the regulator instead of the state commission, and adds NLDC and RLDC coordination on top of the state SLDC.
To encourage inter-state renewable energy trade, ISTS transmission and losses charges are currently waived for solar and wind power sourced through the inter-state network — a policy benefit that does not apply to conventional (thermal) generation moved the same way. This waiver is a major reason ISTS open access can be more competitive for renewable power than it first appears once wheeling and transmission charges are factored in.
The National Load Despatch Centre (NLDC) oversees the national grid; Regional Load Despatch Centres (RLDCs, e.g. SRLDC for the southern region) manage regional scheduling and grid security; and the State Load Despatch Centre (SLDC) handles scheduling within a state. An ISTS open access transaction touches all three, which is why coordination — not just the initial CERC approval — is a meaningful part of the ongoing workload.
Industries
ISTS (inter-state) open access is regulated by CERC, not APERC/TGERC, and applies when power is sourced from outside the state via the inter-state transmission network operated by CTUIL, Power Grid's subsidiary notified as Central Transmission Utility in 2021.
Through the National Single Window System (NSWS), which processes applications in monthly batches — we handle end-to-end filing and coordination with CERC, NLDC, and the regional load despatch centre.
The 100% waiver ended for projects commissioned after 30 June 2025; projects commissioned from July 2025 get a declining waiver stepping down toward 2028, and projects commissioned after 30 June 2028 get no waiver at all.
Yes — BESS co-located with renewables at the same ISTS-connected substation gets a 12-year full ISTS charge waiver, independent of the renewable generation waiver phase-down.
