Sumitomo Corp., through Summit Transition Partners Ltd, a joint venture established with a majority stake held by Sumitomo Corp. and formed with TPK Holdings Co., Ltd, has agreed to invest in multiple large scale battery energy storage system (BESS) projects being developed by Gresham House Energy Storage Fund plc., a leading investor in the UK battery energy storage sector.
In addition, Sumitomo Corp. has entered into a strategic partnership in battery energy storage with Gresham House Ltd (GH), the fund manager of GRID.
In the UK, approximately 50% of electricity sources are supplied by renewable energy, and large scale deployment of BESS is being promoted with policy support to ensure a stable electricity supply. Sumitomo Corp. is already engaged in renewable energy businesses in the UK, including offshore wind, as well as in power trading businesses. Through this initiative and partnership, the company will expand its large scale BESS business and contribute to a more resilient and economically viable power system.
The projects consist of five utility scale BESS projects to be developed across the UK, with a total planned capacity of approximately 694 MW. Construction of the first three projects (total 397 MW), which STP is investing in initially, is scheduled to commence within this fiscal year, while development of the remaining two projects (total 297 MW), over which STP has secured exclusivity rights, will proceed in parallel, enabling the phased expansion of a robust portfolio.
In the UK, the government has set ambitious renewable energy targets, and the role of grid scale BESS, which supports supply-demand balancing and grid stabilisation, is becoming increasingly critical. At the same time, regulatory frameworks supporting the BESS sector are also being strengthened, and demand is expected to expand further in the coming years. Against this backdrop, Sumitomo Corp. has been exploring opportunities in the UK BESS market. In July 2025, the company signed a comprehensive memorandum of understanding (MoU) with the Department for Business and Trade’s Office for Investment under the UK government regarding the promotion of business investment in the UK. This BESS initiative is positioned as one of the projects under the MoU.
As Sumitomo Corp.’s partner in this initiative, GH is a leading developer and operator in the UK BESS sector with a proven track record of developing approximately 1 GW, equivalent to around 15% of the UK’s BESS capacity. By combining GH’s development and operational capabilities with Sumitomo Corp.’s business platform and expertise in BESS, the partners aim to further expand BESS businesses globally, including in the UK, while contributing to stable electricity supply that supports the broader adoption of renewable energy.
Sumitomo Corp. has developed a strong track record across the BESS value chain in Japan, spanning project development, asset ownership, and operational management, including a battery energy storage project on Koshikishiima Island in Satsumasendai City, Kagoshima Prefecture. Furthermore, through its wholly-owned subsidiary, OPTECH Energy Co., Ltd, the company has established advanced capabilities in the optimisation of grid-connected battery storage assets across Japan while leveraging electricity markets to enhance asset performance and create value.
Building on these capabilities, Sumitomo Corp. will combine the expertise developed in Japan with its partnership with GH to expand its battery energy storage business globally, using Japan and the UK as strategic hubs. Through these efforts, the company aims to contribute to the stabilisation of power systems underpinning global energy markets through more resilient and flexible power systems.
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