Solar and storage can supply round-the-clock power at Rs 5.15 per unit, study finds
A study by the India Energy and Climate Centre (IECC) at the University of California, Berkeley, using ten years of hourly weather data across ten Indian states, found that pairing a 3 GW solar plant with 12 GWh of battery storage in Rajasthan can supply firm, round-the-clock (RTC) power at about Rs 5.15 per unit.
This undercuts the recent Solar Energy Corporation of India (SECI) firm and dispatchable renewable energy (FDRE) RTC auction, which discovered winning tariffs of Rs 5.25-5.26 per unit for 1 GW of capacity.
The study's estimate also compares favourably with seven coal power purchase agreements signed in 2025, which ranged from Rs 5.38 to Rs 6.30 per unit.
A "penalty-free" configuration, allowing more compliance headroom, was costed at up to Rs 5.28 per unit; states outside the northwestern cluster (Jammu and Kashmir, Rajasthan, Gujarat) required a slightly larger 3.5 GW solar component paired with the same 12 GWh of storage.
The findings suggest storage-backed solar can already be cost-competitive with both new coal contracts and existing RTC renewable-auction benchmarks without requiring further technology cost declines.
Round-the-Clock (RTC) / Firm and Dispatchable Renewable Energy (FDRE) Tenders
RTC and FDRE tenders are a government procurement design under which renewable-plus-storage projects must supply electricity to a minimum demand-fulfilment profile through the day and night — effectively "mimicking" the reliability of a thermal power plant — rather than supplying power only when the sun shines or the wind blows.
Key Details
- SECI's FDRE-RTC framework requires a minimum demand fulfilment ratio (DFR) of about 90% during peak hours and 80% during off-peak hours (relaxable to 70% for two months between July and September), with an annual DFR requirement of 90%, under 25-year power purchase agreements (PPAs).
- SECI's most recent 1 GW FDRE-RTC tender discovered tariffs of Rs 5.25-5.26 per unit — the benchmark the IECC study's Rs 5.15 estimate undercuts.
- RTC/FDRE tenders are distinct from standalone solar or wind PPAs, which carry no round-the-clock supply obligation.
The study explicitly benchmarks itself against this SECI RTC tariff, showing that a specific solar-plus-storage configuration in Rajasthan could beat the discovered auction price.
Battery Energy Storage Systems (BESS) — Viability Gap Funding (VGF)
Viability Gap Funding is a government financial support mechanism that covers part of the capital-cost gap for infrastructure projects — including Battery Energy Storage Systems — that are not yet commercially viable on tariff revenue alone, to accelerate their deployment.
Key Details
- In March 2024, the Union Cabinet approved the first large-scale BESS VGF scheme, providing ₹3,760 crore in support for 4,000 MWh of battery storage capacity by 2030-31, covering up to 40% of capital cost (about ₹27 lakh per MWh).
- A follow-on scheme extended VGF support to a further 30 GWh of battery storage, backed by ₹5,400 crore from the Power System Development Fund (PSDF), at about ₹18 lakh per MWh.
- Associated measures include a 100% waiver of Inter-State Transmission System (ISTS) charges for storage/renewable energy projects, and a minimum 20% domestic content requirement for VGF eligibility.
The 12 GWh of battery storage modelled in the study is exactly the class of asset the VGF scheme is designed to make commercially viable at scale, reinforcing the study's finding that storage-backed solar can already compete on cost.
India's 500 GW Non-Fossil Capacity Target (Panchamrit, COP26)
The 500 GW non-fossil electricity capacity target by 2030 is one of five climate pledges — collectively termed "Panchamrit" — that India announced at COP26 in Glasgow (2021), alongside meeting 50% of energy requirements from renewables, cutting projected carbon emissions by one billion tonnes, reducing GDP emissions intensity by 45% (over 2005 levels), and reaching net-zero emissions by 2070, all by 2030 or later as specified.
Key Details
- India's updated Nationally Determined Contribution (NDC), submitted to the UNFCCC in August 2022, formally incorporated two of the five Panchamrit elements: a 45% reduction in emissions intensity of GDP by 2030 and 50% cumulative electric power capacity from non-fossil sources by 2030 (the 500 GW absolute figure itself is referenced in national planning documents but was not the number formally submitted to the UNFCCC).
- India has reported crossing 500 GW of total installed power capacity, with non-fossil sources exceeding 50% of that capacity ahead of the 2030 deadline.
- Firm, round-the-clock renewable supply — of the kind modelled in this study — is the technical bridge that allows variable renewables to substitute for coal baseload without compromising grid reliability.
Cost-competitive RTC solar-plus-storage, as the study demonstrates, is the mechanism that lets India scale non-fossil capacity toward and beyond its 500 GW/50% non-fossil target while continuing to meet round-the-clock electricity demand.
- Study: conducted by the India Energy and Climate Centre (IECC), University of California, Berkeley; used 10 years of hourly weather data across 10 Indian states.
- Modelled configuration: 3 GW solar plus 12 GWh battery storage for northwestern states (Jammu and Kashmir, Rajasthan, Gujarat); 3.5 GW solar plus 12 GWh storage for other states.
- Estimated cost: Rs 5.15 per unit (optimal configuration) to Rs 5.28 per unit (penalty-free configuration).
- SECI's 1 GW FDRE-RTC auction winning tariffs: Rs 5.25-5.26 per unit.
- 2025 coal power purchase agreements: Rs 5.38-6.30 per unit.
- BESS Viability Gap Funding: ₹3,760 crore for 4,000 MWh (March 2024 scheme); a follow-on scheme added ₹5,400 crore for 30 GWh.
- India's COP26 "Panchamrit" pledge: 500 GW non-fossil capacity by 2030; India has reported crossing 500 GW total capacity with over 50% from non-fossil sources ahead of schedule.