SECI's latest tender for 1,200 MW of ISTS -connected solar PV projects with 600 MW/3,600 MWh of energy storage systems (ESS) is a clear example of a new transition.
The Solar Energy Corporation of India (SECI) has awarded 1,200 MW of solar capacity bundled with 600 MW/3,600 MWh of energy storage systems at winning tariffs of ₹3.12-3.13 per kWh. Issued in June 2025 as the Tranche-XXI tender, the interstate transmission system (ISTS)-connected projects are structured on a build-own-operate basis to deliver dispatchable, firm renewable power during high-demand periods rather than standard daytime-only generation.
Under the terms of the procurement, developers must integrate at least 0.5 MW/3 MWh of storage capacity for every 1 MW of contracted solar capacity, providing a minimum of six hours of storage duration at rated discharge capacity. Offtakers are permitted to schedule six peak demand hours to draw power, requiring a contracted delivery of 3 MWh per 1 MW of project capacity across the designated timeframe. To ensure compliance with scheduled delivery profiles, SECI has imposed shortfall penalties of up to 1.5 times the project tariff for unsupplied electricity during contracted hours. Developers will sign 25-year power purchase agreements to secure long-term revenue for the assets.
The auction drew strong commercial interest, receiving 24 proposals totaling 6,150 MW—over five times the offered capacity. Following technical and commercial reviews, 23 bidders representing 6,060 MW qualified for the reverse auction. Initial financial bids opened between ₹3.40/kWh and ₹5.40/kWh before competitive bidding drove final prices down to the ₹3.12-3.13/kWh range. Among the winners, Oriana Power secured 100 MW of its 300 MW bid, while three other winning developers received their full requested allocations.
The pricing reflects a substantial drop in costs for time-shifted renewable energy in India. In a comparable 2020 SECI auction for 1,200 MW of peak-power capacity with six hours of storage, Greenko won 900 MW using pumped-hydro storage at approximately ₹6.12/kWh, while ReNew secured 300 MW using battery storage at roughly ₹6.85/kWh. SECI subsequently expanded its hybrid procurement efforts, including a 1,200 MW solar with 1,200 MWh storage tender in 2024, gradually shifting focus toward firm power delivery.
The Tranche-XXI tender specifications remain technology-agnostic, requiring developers to deploy commercially established energy storage systems rather than mandating battery-specific solutions. This flexibility allows participants to utilize various technologies, such as battery energy storage or pumped hydro, to optimize performance, degradation, financing, and delivery obligations over the contract period.
Originally reported by Saur Energy on Sep 14, 2026.
