Storage Goes Bundled: Tamil Nadu's Mandate, China's Joint Bids and Spain's Curtailment

Three recent developments point the same way. Storage is moving from a standalone asset chosen on commercial terms to a condition attached to renewable projects and a participant in market design. Tamil Nadu has written storage into eligibility for new solar and hybrid projects, China's regulator has proposed letting renewable plants and their batteries bid into spot markets as one entity, and Spain's rising curtailment is reshaping how hybrid contracts are priced.

Tamil Nadu makes storage a condition of new renewable capacity

Mercom reports that the Battery Energy Storage Systems Policy, 2026 mandates battery storage for new solar and wind-solar hybrid projects of 1 MW and above, with storage capacity equal to 10% of solar capacity (Mercom India). The source text is brief. It does not set out implementation dates, metering requirements or enforcement mechanisms, so the policy's full scope cannot be confirmed from this report alone.

The instrument matters as much as the threshold. A mandate ties storage to project approval rather than leaving it to developer choice. The same day, Mercom reported that the Gujarat Electricity Regulatory Commission approved tariffs proposed by GUVNL for 450 MW/900 MWh of standalone battery capacity under its Phase IX tender, permitting GUVNL to execute BESPAs with two successful bidders (Mercom India). Taken together, the two states show storage being procured through two routes at once: direct requirements for new renewable hybrids, and competitive tenders for standalone systems.

China proposes letting renewables and storage bid as one

China's National Development and Reform Commission released a draft of Basic Rules for Electricity Spot Markets on October 19. According to ESS News, the draft would replace the 2023 interim rules, with implementation proposed for January 1, 2027, a five-year validity period, and public comments open until November 18 (ESS News).

The central provision is Article 8. It supports renewable plants and their co-located storage participating jointly in bidding, clearing, dispatch, settlement and performance assessment. A solar or wind operator could coordinate generation forecasts and battery charging and discharging schedules when submitting bids, instead of registering generation and storage as separate participants. The report describes two possible effects: shifting deliveries toward higher-priced periods where feasible, and using storage to manage deviations between forecast and actual renewable output, which could reduce imbalance costs.

The draft leaves important questions open. It does not specify detailed bidding formats, metering arrangements, battery charging restrictions or settlement calculations for combined operations. Those details would fall to regional and provincial rules. The report also notes that some provinces, such as Shandong, already operate similar arrangements, so the national draft would formalise practice rather than introduce it from scratch.

Spain shows the economic pressure behind hybrid contracts

The pv magazine report on LevelTen Energy data shows why developers are moving toward hybrid structures. The average standalone solar PPA price in Spain fell to 30.93 euros per MWh in the third quarter of 2026, down 7.7% year on year. LevelTen considers those prices to be approaching the lower limit at which projects can still secure financing. Spanish hybrid solar-and-storage PPAs averaged 48 euros per MWh over the same period (pv magazine).

The report also highlights curtailment. Spanish curtailment reached 2.5 TWh in the first half of 2026, more than three times the volume in the same period of 2025 and 50% above the total for all of 2024. Storage can shift generation to other hours, reducing exposure to low-price periods and limiting the economic effect of curtailment. The data also cautions against overstating the case: hybrid PPA prices rose 6.8% quarter on quarter in Spain but fell 12.7% in Germany, so adding storage does not by itself remove price volatility.

For distribution-level planning, a related example comes from India. ET EnergyWorld reports that Jaipur Discom and GEAPP will test whether sodium-ion battery storage can help manage peak electricity demand locally and improve use of power generated by rooftop solar installations (ET EnergyWorld).

What it means for utilities

For DISCOMs and network operators, the common thread is that storage is becoming part of the commercial and regulatory structure of renewable generation, not only a separate procurement line. Three implications stand out.

First, forecasting and dispatch data become more valuable. Joint bidding depends on coordinated forecasts and battery schedules, and imbalance costs depend on how accurately forecast deviations are measured and settled. Utilities that cannot access or validate this data will have difficulty assessing hybrid bids or local flexibility.

Second, metering and settlement rules are the unresolved layer. The Chinese draft explicitly leaves metering and settlement to lower levels of government. Indian states that adopt storage mandates will need to define how co-located storage is metered, how charging from grid or from the plant is distinguished, and how performance is verified.

Third, curtailment is a signal about where flexibility is needed. Spain's curtailment figures show that rapid renewable build-out without matching flexibility can waste generation. Storage tied to specific feeders or rooftop clusters, as in the Jaipur test, offers a more granular way to absorb that output.

Key takeaways

• Tamil Nadu requires storage equal to 10% of solar capacity for new solar and wind-solar hybrid projects of 1 MW and above, while Gujarat procures standalone storage through tenders.
• China's draft spot-market rules would let renewable plants and on-site batteries bid jointly, with implementation proposed for January 1, 2027 and comments open until November 18.
• Key details on bidding formats, metering, charging restrictions and settlement are deferred to regional and provincial rules.
• Spain's curtailment reached 2.5 TWh in the first half of 2026, while hybrid PPAs averaged 48 euros per MWh against 30.93 for standalone solar.
• Storage does not automatically remove price volatility, so market and settlement design will determine outcomes.

Sources

• Tamil Nadu Mandates Battery Storage for New Solar, Hybrid Projects
• Gujarat Approves Tariffs for 450 MW/900 MWh Battery Storage Projects
• China outlines new spot market rules supporting renewable energy and storage integration
• Spain solar PPA prices fall to €30.93/MWh as BESS gains ground
• Jaipur Discom, GEAPP to test use of sodium-ion battery energy storage system for power supply