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").

21 May 2026

Invinity Energy Systems plc

("Invinity" or the "Company")

Invinity Selected to Design GWh-Scale VFB System

Strategic Partnership with FlexBase to Develop World's Largest Flow Battery

Invinity Energy Systems plc (AIM: IES), a leading global manufacturer of utility-grade energy storage, is delighted to note FlexBase Group's announcement that, following an in-depth competitive selection process that reviewed proposals from flow battery manufacturers from across the world, it has selected Invinity to design a GWh-scale vanadium flow battery ("VFB") for deployment at the Technology Centre Laufenburg.

Image: Representatives from FlexBase and Invinity at the project site in Laufenburg, Switzerland. From left to right: Pascal Wyss (CIO, FlexBase), Marcel Aumer (Group CEO & Founder, FlexBase), Jonathan Marren (CEO, Invinity), Jean-Louis Cols (VP, Global Partner Development, Invinity), Ben Williams (Project Manager, Invinity)

Situated in the Swiss municipality of Laufenburg, which is located on the Switzerland-Germany border, the project will feature an AI datacentre and technology campus, integrated with a VFB of up to 1.5 GWh capacity - believed to be the world's largest to date. Invinity's battery solution, which FlexBase will look to expand to 2.1 GWh in subsequent phases, will be used to support the integration of renewable energy onto the site and provide stabilisation to the grid.

Image: Construction progress at the Laufenburg site (left) and team members from Invinity and FlexBase conducting a site inspection (right)

The project broke ground in May 2025 and is currently under construction. Invinity will now proceed with the engineering phase of the project, which is expected to take place during 2026 and into 2027 and will generate engineering revenue for the Company, subject to the achievement of various development milestones. Following the successful conclusion of the engineering design phase, a purchase order for the battery system is anticipated to be received, allowing Invinity to initiate phased manufacturing of datacentre-optimized VFB modules for integration into the project.

Further announcements will be made in due course as the project progresses.

Marcel Aumer, Group CEO, Chairman of the Board and Founder of FlexBase Group said:

"Invinity has proven to be the strongest partner by presenting the most compelling overall package with the lowest life-cycle costs (LCOS). Invinity's vanadium flow technology is perfectly suited for our project due to its safety - particularly its non-flammability - its cycle stability, and its flexibility in application."

Pascal Wyss, Chief Innovation Officer at FlexBase said:

"In Invinity, we have found a partner that not only possesses market-ready and internationally proven technology but has also impressed us with innovative, modular solutions perfectly tailored to FlexBase. We look forward to working with the Invinity team to advance the vision of a sustainable energy future."

Jonathan Marren, Chief Executive Officer at Invinity said:

"Having just delivered the biggest vanadium flow battery in the UK, Invinity now enters the engineering phase of what will be the world's largest vanadium flow battery to date. Our longstanding focus on continually building our expertise in flow battery technology has been recognized with the award of this phase of the contract and I am extremely proud of the efforts of the Invinity team in getting us to this position."

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Notes to Editors

Invinity Energy Systems plc (AIM: IES) is a world-leading manufacturer of vanadium flow batteries (VFB). Built in our factories in the UK and Canada, the Company's proven energy storage technology has been deployed at scale and dispatched gigawatt-hours of electricity for customers across the world to date.

Invinity's safe, scalable and durable battery technology is a trusted and safer alternative to lithium-ion batteries and our VFBs are engineered for heavy-duty, high throughput applications. They don't wear out, cannot catch fire and are designed to be operated for 30 years or more. Our products address the challenges of our global energy system by delivering energy storage without limits, unlocking low-cost, low-carbon power on-demand.

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].