Japan’s association of grid operators has selected 19 battery storage projects totalling 1,251MW in the third running of a national capacity market auction.
The Organisation for Cross-regional Coordination of Transmission Operators (OCCTO) announced the results of its Long-Term Decarbonisation Power Sources Auction (LTDA) last week (13 May).
It’s the third annual staging of Japan’s supplemental capacity market auction, which runs in addition to the main capacity market auctions. While the main auction seeks to secure capacity to ensure security of supply in the immediate years, the LTDA instead aims to add longer-term sources of clean energy capacity to the grid.
LTDA projects were awarded 20-year fixed-revenue contracts for capacity delivery beginning in FY2027.
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While the previous round’s 1.3GW of battery storage winners, announced in April 2025, comprised a mix of 3-hour and 6-hour duration projects, this time out, eligibility was limited to projects planned for 6-hour duration and above.
This, coupled with a new cybersecurity certification system, JC-STAR, and domestic content rules that mean no more than 30% of awarded battery capacity uses cells manufactured in any single foreign country, is thought to have resulted in the latest round seeing a lower number of bids than before.
Alongside the BESS projects, 453MW of contracts were awarded to two pumped hydro energy storage (PHES) projects, 264MW to ammonia co-firing, 253MW to hydrogen-only generation, 101MW to biomass, 1.38GW to new or refurbished nuclear capacity, 558MW to upgrading nuclear plants and 3GW for LNG thermal power.
Total bid capacity was 10.9GW, of which 67% was successful.
Solar developer Hexa Energy Services recently celebrated putting Japan’s first project with an LTDA contract into commercial operation. A completion ceremony was held in March for Hexa’s 30MW/130MWh Tagawa BESS project, for which the company won a contract in the FY2023 LTDA, part of a total 455MW of wins across 11 projects for the developer in that round.
Previous winners Stonepeak, CHC, Bison Energy and Hexa back for more
While results published by OCCTO take care to obscure individual company names, a couple stood out as winners of previous auctions.
A subsidiary of US investor Stonepeak won at least three contracts, for 95.6MW, 45.9MW and 32.8MW of capacity at three projects. Stonepeak entered Japan’s BESS market in 2024, enticed by the country’s fundamental need for energy storage and a supportive policy environment.
Stonepeak’s joint development bids with Singaporean BESS developer CHC won 348MW of contracts in the previous, second round of the LTDA. Partner CHC was named in OCCTO’s latest results as the winner of contracts for two BESS projects, one for 75.6MW capacity and the other for 36.7MW.
Japan-headquartered renewables developer Bison Energy said in a press release that it had won contracts for 141.5MW and 140MW of capacity at two projects. Like Stonepeak and CHC, Bison Energy was also a winner in last year’s auction round.
Hexa Energy Services was also identifiable from the list of FY2025 awarded projects, with a 46.9MW contract and a 43.5MW contract.
“We are very pleased that two of our grid-scale BESS projects in the Chugoku and Tohoku areas, totalling 90.47MW, have been selected in the FY2025 Long-Term Decarbonisation Power Source Auction,” Hexa Energy Services said.
“As renewable energy deployment continues to expand, grid-scale battery energy storage systems are becoming increasingly important power infrastructure, particularly in light of growing uncertainties in the energy environment, including rising energy costs and concerns over stable supply. BESS plays a critical role in balancing electricity supply and demand, alleviating grid congestion, and stabilising power supply. Projects selected through the auction are also expected to contribute to reducing the public cost burden associated with grid stabilisation.”
Energy-Storage.news publisher Solar Media (part of the Informa Group) will host the Energy Storage Summit Asia 2026 on 1-3 July at QSNCC, Bangkok, Thailand. The conference takes place during ASIA Sustainable Energy Week 2026 (ASEW), the region’s most influential platform for driving clean energy. For more information, visit the official website.
