Key Takeaways
- Agency: Solar Energy Corporation of India (SECI)
- Auction: SECI-ISTS-XXI (ISTS-Connected Solar with Energy Storage)
- Solar capacity: 1,200 MW
- Storage capacity: 600 MW / 3,600 MWh
- Results announced: January 10, 2026
- Tariff range: Rs 3.12 to Rs 3.13 per kWh
- Winners: Engie (200 MW), NLC India (600 MW), RPIL Power Three (300 MW), Oriana Power (100 MW)
- RfS issued: June 19, 2025
What Is This Auction?
Solar Energy Corporation of India (SECI) announced the results of its ISTS-XXI auction on January 10, 2026 — one of the first major solar-plus-storage auction results of 2026. The auction procured 1,200 MW of ISTS-connected solar power paired with 600 MW/3,600 MWh of energy storage, at competitive tariffs of Rs 3.12–3.13 per kWh.
This is part of SECI's ongoing series of ISTS-connected solar auctions that have been the backbone of India's utility-scale solar procurement since 2019. What distinguishes ISTS-XXI is the integrated energy storage requirement — each winning developer must pair their solar generation with proportionate battery energy storage, making the contracted power more dispatchable and grid-friendly.
The auction attracted "strong interest from developers," reflecting the maturity of India's solar-plus-storage market and the commercial viability of battery storage at current prices.
Auction Winners and Tariffs
| Developer | Capacity Awarded | Tariff (Rs/kWh) |
|---|---|---|
| Engie Energy India | 200 MW | Rs 3.12 |
| NLC India Renewables | 600 MW | Rs 3.12 |
| RPIL Power Three | 300 MW | Rs 3.12 |
| Oriana Power | 100 MW | Rs 3.13 |
| Total | 1,200 MW solar + 600 MW/3,600 MWh storage |
NLC India Renewables — the renewable energy arm of NLC India Limited (National Lignite Corporation) — is the largest winner with 600 MW. NLC has been aggressively expanding its renewable energy portfolio (it also won 300 MW in GUVNL's 625 MW auction at Rs 2.34/kWh), making it one of India's most active public sector renewable energy developers in 2025–26.
Engie Energy India is the Indian subsidiary of France's Engie Group, a global energy company with significant renewable energy presence in India including wind, solar, and green hydrogen projects.
RPIL Power Three is likely a special purpose vehicle (SPV) created for this specific project. Many renewable energy developers create project-specific SPVs for large tenders.
Oriana Power is an Indian clean energy developer and EPC company that has been expanding its portfolio through SECI auctions.
Integrated Energy Storage Requirement
The defining feature of SECI-ISTS-XXI is the mandatory integrated energy storage system. Each winning developer must build and operate battery energy storage systems proportionate to their solar capacity:
- Storage ratio: 600 MW/3,600 MWh storage for 1,200 MW solar = 0.5 MW/3 MWh per MW of solar
- Storage duration: 6 hours (3,600 MWh / 600 MW)
This 6-hour storage duration is significant — it means solar power generated during peak afternoon hours can be stored and dispatched during the evening peak demand period (typically 6 PM to 10 PM), when solar generation has already ended for the day.
The integrated storage requirement means:
- Developers must source and integrate battery storage alongside solar panels
- Project costs and tariffs are higher than pure solar (Rs 3.12–3.13/kWh vs Rs 2.34–2.87/kWh for pure solar in recent auctions)
- The resulting power is more valuable to the grid and to SECI's offtakers because it is partially dispatchable
What Rs 3.12/kWh Means: Solar Plus Storage Tariff Benchmarks
The Rs 3.12–3.13/kWh tariff for solar-plus-6-hour-storage is an important market benchmark. Comparing across recent SECI auctions:
| Auction | Type | Storage Duration | Tariff |
|---|---|---|---|
| SECI Tranche XX (Oct 2025) | Solar only (ISTS) | None | Rs 2.86–2.87/kWh |
| SECI Tranche XXI (Jan 2026) | Solar + 6hr BESS | 6 hours | Rs 3.12–3.13/kWh |
| SECI FDRE Tranche VII (2026) | Firm/Dispatchable RE | Variable | Rs 3.12+ (ACME) |
The premium for 6-hour storage over pure solar is approximately Rs 0.25–0.26/kWh — reflecting the cost of battery storage at current market prices. This premium has been declining steadily as battery pack costs have fallen from over $300/kWh in 2020 to below $100/kWh in 2025–26.
Why Solar-Plus-Storage Matters for India's Grid
India's rapid solar expansion — 44.6 GW added in FY2026, with 150 GW of cumulative solar capacity as of March 2026 — has created a "duck curve" challenge on the grid: solar generation peaks between 10 AM and 3 PM, but electricity demand peaks in the evening (6–10 PM). Without storage, the grid must ramp up thermal plants rapidly in the evening, increasing costs and carbon emissions.
Integrated solar-plus-storage projects like SECI-ISTS-XXI directly address this challenge by:
- Shifting solar generation from the afternoon generation peak to the evening demand peak
- Reducing grid operator costs by eliminating the need for costly peaking thermal plants in the evening
- Improving renewable energy utilisation by avoiding curtailment of excess afternoon solar generation
- Supporting grid stability with battery systems providing ancillary services (frequency regulation, voltage support)
For India's 500 GW renewable energy target by 2030, large-scale storage integration of this type is not optional — it is essential.
What This Means for Industrial Solar Buyers
For industrial consumers evaluating their energy procurement options, SECI-ISTS-XXI signals several important trends:
Storage costs are coming down: The Rs 3.12/kWh solar-plus-6-hour-storage tariff (compared to Rs 2.86/kWh for pure solar) implies a storage cost premium of approximately Rs 0.25/kWh. Industrial buyers considering solar-plus-storage for their own facilities should note that behind-the-meter storage costs have also declined, making solar-plus-storage viable for businesses with evening electricity demand.
Dispatchable solar is commercially real: Earlier concerns about battery storage reliability and economics are increasingly moot. Four credible developers (Engie, NLC, RPIL, Oriana) have committed to 25-year contracts at Rs 3.12–3.13/kWh for solar-plus-storage — demonstrating commercial confidence in the technology.
Industrial buyers with evening/night loads — manufacturing plants running second and third shifts — can explore solar-plus-storage for captive projects, extending solar coverage from daytime-only to 24-hour supply with appropriate storage sizing.
For EPC companies serving industrial clients, the growing market for solar-plus-storage at the utility scale creates technology and supply chain maturity that benefits commercial and industrial storage projects. Battery prices, integration expertise, and monitoring systems developed for utility-scale projects flow into smaller commercial applications.
For more on evaluating solar-plus-storage for your industrial facility, see our guides on solar battery storage for industrial use in India and comparing solar, diesel generator, and battery backup options.
About SECI's ISTS Solar Tender Series
SECI's ISTS-connected solar tender series has been the primary vehicle for India's utility-scale solar procurement since 2019. Each "Tranche" procures a specific capacity of solar power from projects connected to the interstate transmission network, allowing developers to site plants anywhere in India. By Tranche XXI in January 2026, the series has collectively procured tens of GW of solar capacity and has progressively incorporated storage requirements as battery costs have fallen. SECI-ISTS-XXI's 1.2 GW scale with 3.6 GWh of storage represents the maturation of this procurement series into the storage era.
Frequently Asked Questions
What is SECI-ISTS-XXI?
SECI-ISTS-XXI is the 21st tranche of SECI's Interstate Transmission System-connected solar power tender series. It procured 1,200 MW of solar power paired with 600 MW/3,600 MWh of battery energy storage from four developers at tariffs of Rs 3.12–3.13 per kWh.
Why is the tariff higher than pure solar auctions?
The Rs 3.12–3.13/kWh tariff reflects the additional cost of 6-hour battery energy storage integrated with the solar project. Pure solar ISTS auctions (like Tranche XX) discovered Rs 2.86–2.87/kWh. The approximately Rs 0.25/kWh premium is the cost of storage — which has been declining as battery prices fall.
Who is NLC India and why did it win 600 MW?
NLC India Renewables is the renewable energy subsidiary of NLC India Limited (National Lignite Corporation), a Central Public Sector Enterprise under the Ministry of Coal. NLC has been diversifying aggressively into renewables — winning 300 MW in GUVNL's Gujarat auction and now 600 MW in SECI-ISTS-XXI. Its strong financial backing as a CPSE and aggressive bidding strategy make it competitive across multiple auctions.
When will projects under SECI-ISTS-XXI be commissioned?
Auction details did not specify commissioning timelines. Standard SECI ISTS tender terms require supply commencement within 18–24 months of PPA signing. Given the January 2026 results, commissioning would be expected around mid-2027 to early 2028.
How does 3,600 MWh of storage compare to India's total BESS capacity?
India added approximately 4.6 GWh of energy storage capacity in Q1 2026 alone — reflecting a massive surge in BESS deployment. The 3,600 MWh from SECI-ISTS-XXI represents a significant but no longer exceptional addition to India's rapidly growing storage fleet.
Sources
- SECI Awards 1.2 GW ISTS-Connected Solar-Plus-Storage Projects to Engie, NLC, RPIL, Oriana at Rs 3.12–3.13/kWh — SolarQuarter (January 10, 2026)
- ENGIE, NLC India, Rays Power Among Winners of SECI's 1.2 GW Solar Plus 3.6 GWh Storage Auction — Scanx Trade
- Daily News Wrap-Up: India Adds 4.6 GWh Energy Storage Capacity in Q1 2026 — Mercom India
- India Added Record 15.3 GW Solar Capacity in Q1 2026 — PV Magazine India
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