The information contained within this Announcement is deemed by Invinity Energy Systems plc to constitute inside information as stipulated under the Market Abuse Regulation (EU) No. 596/2014 as it forms part of UK law by virtue of the European Union (Withdrawal) Act 2018 ("MAR").

22 December 2025

Invinity Energy Systems plc

("Invinity" or the "Company")

12 MWh Sale for U.S. Project

Endurium battery system to be deployed at PNNL's Richland, Washington campus

Invinity Energy Systems plc (AIM: IES) (OTCQX: IESVF), a leading global manufacturer of utility-grade energy storage, is pleased to announce the sale of a 12 MWh Endurium battery system to Pacific Northwest National Laboratory ("PNNL").

The batteries will be installed at PNNL's Richland, Washington campus and used to demonstrate the ability of advanced energy storage in general, and Invinity's vanadium flow batteries ("VFBs") in particular, to deliver the durable, flexible services needed for a future low-cost, high-reliability electrical grid. In proving their ability to provide 24-hour energy discharge, improve operational resilience and decrease peak site energy demand, Invinity's VFBs are expected to further deliver significant benefits to PNNL.

This sale follows the recent inauguration visit by U.S. Energy Secretary Chris Wright to PNNL's Grid Storage Launchpad, where he initiated the testing of an Invinity battery. This comes at a time when energy storage continues to gain prominence within the U.S. power market as grid operators begin to prioritise storage duration over short-term capacity. For example, PJM, the largest grid operator in the U.S., is elevating the priority of eight- and ten-hour duration systems as it looks to support new resources that can balance load and deliver energy when its system is potentially at risk.

As previously announced by the Company in September 2023, this project is supported by funds from the U.S. Department of Energy which were made available to a number of U.S. projects which plan to feature Invinity's technology. Delivery of the Invinity batteries is expected in H2 2026.

Matt Harper, President at Invinity said:

"From its very beginnings, PNNL has been one of the most innovative laboratories in energy, pioneering the technologies and solutions that form the backbone of today's electric grid in every corner of the globe.

"Invinity is thrilled to be providing one of the main components of PNNL's most recent facility, the Grid Storage Launchpad, to prove how our safe, durable, long duration vanadium flow batteries can help enhance the future electric grid. The inherent characteristics of our proven technology, including its ability to deliver both instantaneous demand response and extended discharge durations over decades of service, makes it the ideal solution for maximising this potential.

"With the support and engagement of the Department of Energy, we look forward to working with PNNL's researchers to guide the technology, policy and regulation that will enhance the role that Invinity's vanadium flow batteries can play on our future electric grid, in the U.S. and beyond."

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Notes to Editors

Invinity Energy Systems plc (AIM: IES) (OTCQX: IESVF) manufactures vanadium flow batteries for large-scale, high-throughput energy storage requirements of business, industry and electrical networks.

Invinity's factory-built flow batteries run continually with no degradation for over 30 years, making them suitable for the most demanding applications in renewable energy production. Energy storage systems based on Invinity's batteries are safe, reliable, and economical, and range in size from 1 to hundreds of megawatt-hours.

Invinity was created in April 2020 through the merger of two flow battery industry leaders: redT energy plc and Avalon Battery Corporation. With more than 190 MWh of systems deployed, contracted for delivery or awarded for projects across more than 90 sites in 17 countries, Invinity is active in all major global energy storage markets and has operations in the UK, Canada, USA and China. Invinity Energy Systems plc is quoted in the UK on AIM and trades in the USA on OTCQX.

To find out more, visit invinity.com, sign up to our monthly Investor Newsletter here or contact Investor Relations on via +44 (0)20 4551 0361 or [email protected].