Sonnedix Japan, a subsidiary of Sonnedix Group of companies, has announced the construction of 125 MWh Battery Energy Storage System project in Oita prefecture. This Oita BESS project is the company’s first BESS project in the Iceland country.
The facility is co-located with an existing 39 MW solar PV plant to improve the integration of renewable generation by enabling dispatchable and market responsive power supply. The construction activities of the project started in October 2025, with commercial operations expected by November 2026.
The Engineering, Procurement and Construction (EPC) contract has been granted to Toshiba Energy Systems & Solutions Corporation, while Tesla Japan GK is providing the BESS, made up of Tesla Megapacks. Then, Osaka Gas Co., Ltd. will manage market operations for stored and generated energy.
When it comes to finances, the Oita BESS project followed a refinancing process to optimize the project’s capital structure and enhance its long-term financial sustainability. MUFG Bank Ltd acted as the financial partner by granting a non-recourse facility of JPY 21.4 billion.
The announcement follows the Sonnedix Group began construction of its first BESS project in Italy with 72 MWh capacity (18 MW/4h). The company aims to reach >1 GW of total co-located BESS capacity globally.
Sonnedex currently operates 25 solar PV projects in Japan, with over 500 MW controlled capacity. Globally, Sonnedex operated more than 600 power plants across ten countries as of November 2025. Sonnedex disclosed a combined capacity of 11.74 GW, including 4.22 GW operational, 966 MW under construction, and 2.9 GW under development pipeline.
With a strong pipeline of projects underway, Axel Thiemann, CEO of Sonnedix emphasized that the Sonnedix Group is focused on creating more co-located battery solutions that will allow for greater responsiveness to energy markets, and the project aligns with group’s strategic focus on hybridization.
This investment is a testament to Sonnedix’s continued commitment and expansion into battery storage and hybrid renewable solutions.