Sumitomo Corporation and Gresham House, One of Europe’s Largest Battery Energy Storage Investors, to Establish a New Large-Scale BESS Portfolio- Entered into Strategic Partnership in UK Grid-Scale Battery Energy Storage -

Sumitomo Corporation (Head Office: Chiyoda-ku, Tokyo; Representative Director, President and Chief Executive Officer: Shingo Ueno), through Summit Transition Partners Limited (“STP”), a joint venture established with a majority stake held by Sumitomo Corporation and formed with TPK Holding Co., Ltd. (Head Office: Taipei, Taiwan; Chairman: Michael Chao-Juei Chiang; hereinafter “TPK”), has agreed to invest in multiple large-scale battery energy storage system (“BESS”) projects (the “Projects”) being developed by Gresham House Energy Storage Fund plc (Head Office: London, UK; Chair: John Leggate CBE; hereinafter “GRID”), a leading investor in the UK battery energy storage sector. In addition, Sumitomo Corporation has entered into a strategic partnership in battery energy storage with Gresham House Limited (“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 Corporation 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.

Project Overview

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 397MW), which STP is investing in initially, is scheduled to commence within this fiscal year, while development of the remaining two projects (total 297MW), over which STP has secured exclusivity rights, will proceed in parallel, enabling the phased expansion of a robust portfolio.

Background of the Business Participation

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 stabilization, 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 Corporation has been exploring opportunities in the UK BESS market. In July 2025, the company signed a comprehensive memorandum of understanding 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 memorandum of understanding.

As Sumitomo Corporation’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 Corporation’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 Corporation’s Initiatives in Battery Energy Storage

Sumitomo Corporation 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, and an EV battery station business in Chitose City, Hokkaido. 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 Corporation 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 stabilization of power systems underpinning global energy markets through more resilient and flexible power systems.

Overview of Summit Transition Partners Limited (STP)

Overview of Gresham House Energy Storage Fund plc (GRID)

Overview of TPK Holding Co., Ltd.

Project Portfolio and Locations