Japan-based Sumitomo Corporation, through Summit Transition Partners (STP), has announced an investment in multiple utility-scale battery energy storage system (BESS) projects in the UK being developed by Gresham House Energy Storage Fund (GRID). Alongside the investment, Sumitomo Corporation has also entered into a strategic partnership in battery energy storage with Gresham House (GH), the fund manager of GRID.
STP is a joint venture established with a majority stake held by Sumitomo Corporation in partnership with Taiwan-headquartered TPK Holding.
The portfolio comprises five utility-scale BESS projects across the UK with a combined planned capacity of approximately 694 MW. Of these, the first three projects with a total capacity of 397 MW are expected to begin construction within the current fiscal year. STP will initially invest in these projects, while also securing exclusivity rights for the remaining two projects, totalling 297 MW, enabling phased portfolio expansion.
The development comes as the UK continues to accelerate renewable energy integration, with nearly half of the country’s electricity generation currently sourced from renewables. The deployment of large-scale battery storage systems is being actively supported to strengthen grid stability and ensure a reliable power supply amid increasing renewable penetration.
Sumitomo Corporation stated that the initiative aligns with its broader renewable energy and power trading operations in the UK, including offshore wind businesses. Through the partnership with Gresham House, the company aims to expand its large-scale BESS portfolio and contribute to building a more resilient and economically sustainable power system.
The company highlighted that the UK government’s renewable energy ambitions and evolving regulatory frameworks are expected to further drive demand for grid-scale energy storage. Sumitomo Corporation had earlier signed a comprehensive memorandum of understanding in July 2025 with the UK government’s Department for Business and Trade Office for Investment to promote business investments in the UK, with the current BESS initiative positioned under this framework.
Gresham House has developed around 1 GW of battery storage capacity, representing nearly 15 percent of the UK’s total BESS capacity. The partnership will combine Gresham House’s operational and development expertise with Sumitomo Corporation’s experience in battery storage and energy market optimisation.
Sumitomo Corporation has built a diversified BESS portfolio in Japan covering project development, ownership and operational management. Its projects include a battery storage installation on Koshikishima Island in Kagoshima Prefecture and an EV battery station business in Hokkaido. Through its wholly owned subsidiary OPTECH Energy, the company also operates grid-connected battery storage optimisation businesses in Japan.
Going forward, Sumitomo Corporation plans to leverage its experience from Japan alongside the UK partnership with Gresham House to expand its battery storage operations globally, positioning Japan and the UK as strategic hubs for future growth in flexible energy infrastructure.
