,

, RPIL Power Three (

), and

won Solar Energy Corporation of India’s (

) Tranche XXI auction to set up 1,200 MW of interstate transmission system (ISTS)-connected solar projects integrated with 600 MW/3,600 MWh energy storage systems (ESS).

Engie Energy India and NLC India Renewables won 200 MW and 600 MW, respectively, at a quoted tariff of ₹3.12 (~$0.0346)/kWh.

RPIL Power Three quoted a tariff of ₹3.13 (~$0.0347)/kWh to win 300 MW.

Oriana Power quoted 300 MW to win 100 MW under the bucket-filling method at a tariff of ₹3.13 (~$0.0347)/kWh.

The tender was

in June 2025.

The projects include the development of solar projects, each co-located with an ESS. It also involves land acquisition, project development, and all necessary ISTS/ state transmission unit grid interconnections.

The ESS must be physically situated at the solar project sites. Each ESS must be at least 0.5 MW/3 MWh for each 1 MW project capacity. The winners can change the ESS technology at any time during the power purchase agreement (PPA) period.

The projects must be commissioned within 24 months from the effective date of the power purchase agreement (PPA), with an additional six-month window for delays. The PPA tenure is 25 years.

The winners must use modules that meet the domestic content requirement and adhere to the Approved List of Models and Manufacturers.

The projects can be set up with any storage technology in any location in India, provided the winners ensure the availability of ISTS connectivity.

The project must maintain an annual capacity utilization factor between 19% and 30%.

The buying entity will purchase power for 6 hours during the peak hours from 6 PM to 9 AM of the subsequent day. The ESS must continuously supply power for at least 1 hour.

The projects must deliver 3,000 kWh of energy per MW of project capacity during the peak hours.

Winners can supply up to 5% of their annual energy from power exchanges and bilateral agreements.

The projects must use commercially established and operational technologies to minimize technology risk and achieve timely commissioning.

In October 2025, eleven companies

SECI’s Tranche XX auction to set up 2GW of ISTS-connected solar projects, along with 1GW/4GWh ESS.

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