How RUMSL Differs from NHPCs Solar + BESS Tender
The Curious Case of RUMSL’s Solar + Storage Auction: Lessons Beyond the Low Tariffs
The recently concluded 600 MW Solar + Storage auction by Rewa Ultra Mega Solar Ltd. (RUMSL) marks another milestone in India’s renewable energy journey.
With discovered tariffs between ?2.70–?2.76/kWh, the results appear impressive at first glance — but a deeper analysis reveals critical insights and risks that developers, lenders, and policymakers must consider.
How RUMSL Differs from NHPC’s Solar + BESS Tender
Unlike NHPC’s Solar + BESS model, which rewarded incremental generation, RUMSL’s structure capped the upside for developers.
Here’s what makes it distinct:
No incentive for higher capacity utilization:
Power generation beyond 220 MW (up to 300 MW) is compensated at only ?2.15/kWh, making overbuilds financially unattractive.
The unique advantage – free charging power:
The MPPMCL offers free night-time charging, allowing developers to store energy and sell it back during the 9-hour peak window.
With a Round Trip Efficiency (RTE) above 85%, even excess stored energy earns ?2.15/kWh — partially offsetting the tariff pressure.
Strict performance rules:
Developers must maintain 95% peak availability and a 35% CUF, backed by stringent penalties, keeping execution risk high despite RUMSL managing land and evacuation.
The Developer’s Balancing Act
To meet both morning (4-hour) and evening (5-hour) peak demands, developers must design precise storage and dispatch strategies.
Overdesign reduces profitability, while underdesign increases penalty risk.
Though RUMSL reduces construction complexity, the capped upside leaves little financial cushion against shocks or delays.
Why the Tariffs Are Risky
Despite appearing competitive, the discovered tariffs push the limits of project viability:
Sustainable range:
Realistic tariffs should hover around ?3.00/kWh.
Even under aggressive cost and financing assumptions, ?2.85–?2.95/kWh is the lower feasible boundary.
Margin erosion:
Bidding below this range exposes developers to serious financial stress.
Cost volatility:
A mere 5% fluctuation in module or battery prices can wipe out profits.
Financing challenges:
Projects might clear technical evaluation but struggle to meet financial closure due to weak returns.
Lower irradiation:
Unlike Rajasthan’s high-GHI solar zones, Morena experiences lower irradiation, reducing generation potential and straining economics.
Why This Matters for India’s Energy Transition
For India to achieve a stable renewable future, dispatchable solar power with integrated storage is crucial.
However, replicable and bankable tender models are essential — not just one-off record-low bids that look good on paper but struggle in execution.
Conclusion
The RUMSL Solar + Storage auction represents both a bold leap forward and a cautionary tale.
While innovation and ambition continue to define India’s renewable energy trajectory, tariffs must align with ground realities to ensure long-term sustainability.
Otherwise, projects that shine at commissioning may prove fragile over time.