Japan’s largest renewable battery energy storage system (BESS) project has broken ground in Kyushu spearheaded by developers, Osaka Gas and Sonnedix. The construction will install a 125 MWh battery energy storage in Oita Prefecture. Japan’s largest renewable battery storage project will be co-located with Sonnedix’s 30 MW AC/38.6 MW DC solar power facility. It is expected to enhance grid stability and improve dispatch flexibility. Commissioning of the BESS project is slated for late 2026.
Project Overview
Toshiba Energy Systems & Solutions Corporation serves as EPC contractor for Japan’s largest renewable BESS project, while Tesla Japan will supply Megapack units to enable large-scale energy storage. Once operational, the battery storage facility will store surplus solar generation during off-peak hours and release the energy when demand is high – as with all BESS installations.
Wholesomely, the renewable battery storage project forms part of a growing collaboration between Osaka Gas and Sonnedix in Japan’s transition toward a low carbon energy mix. Japan’s low carbon energy mix is also making great strides as Fukushima nuclear plant eyes restart after the Chernobyl-level 2011 accident. These concerted efforts also continue to support the East Asia country’s decarbonization goals under the Green Transformation (GX) initiative.
Project Factsheet for Japan’s Largest Battery Energy Storage (BESS) Project by Sonnedix and Osaka Gas
Name: Sonnedix-Osaka Oita BESS Project
Location: Oita Prefecture in Japan’s third largest island, Kyushu
Project Type: Battery storage co-located with solar PV
Capacity: 125 MWh battery storage, and 30 MW AC/38.6 MW DC solar capacity
Developers: Sonnedix Japan and Osaka Gas
Technology Supplier: Tesla for Megapack units
EPC Contractor: Toshiba Energy Systems & Solutions Corporation
Investment Cost: Approx. 21.4 billion yen (US$ 139 million). BESS installation costs in Japan are around ¥62,000 per kWh, excluding tax.
Start of Construction: October 2025
Commissioning Date: 2026
Ownership: Sonnedix is majority owner. Osaka Gas will manage market dispatch.
Significance: Japan’s largest renewable-integrated BESS project. Also Sonnedix Japan’s first storage deployment.
Project Timeline
2023-2024: Feasibility studies and regulatory clearance under the Ministry of Economy, Trade and Industry (METI).
March 2025: Partnership between Sonnedix and Osaka Gas for joint battery project development.
October 2025: Sonnedix and Osaka Gas break ground on Japan’s largest renewable battery energy storage (BESS) project. Contracts also include Toshiba Energy Systems and Tesla.
2026: Expected start of commercial operations for the project.
What Lies Ahead for Japan’s Largest Battery Storage (BESS) Project by Sonnedix and Osaka Gas in Kyushu
Sonnedix’s involvement in this project points to its broader Asia-Pacific growth strategy. The company is targeting over 2 GW of renewable portfolio in Japan by 2030. Osaka Gas will also lean on its energy market trading experience for returns from the battery storage project. This is also expected to support Japan’s balancing market introduced in 2021.
Looking ahead, Sonnedix and Osaka Gas are also expected to expand their cooperation for additional battery storage assets across the country. This could favorably be in regions like Hokkaido and Tohoku which have witnessed growing solar penetration but with constrained grid capacity. Some of Japan’s 2020s solar installations include the Onikoube solar power project, Kuwabarajo Mega Solar No.4, and the Kanoya Osaki solar hills farm also Kyushu.
