METLEN and Karatzis Group of Companies are entering into a new strategic partnership through a joint venture for the development, construction, operation, and energy management of a Battery Energy Storage System (BESS) with a capacity of 330MW / 790 MWh in Thessaly, Greece. The partnership establishes ownership stakes of 49% for METLEN and 51% for Karatzis Group.

This project will be the largest standalone storage unit planned to date in Greece and one of the biggest in Europe. The announcement was made on October 9, 2025, from Athens, Greece, and London, United Kingdom.

Project Investment and Timeline

The total investment for this project amounts to around EUR 170 million. The project is expected to be completed within the second quarter of 2026. No further grants or tax reliefs are expected for this project. METLEN will undertake the complete construction, operation, and maintenance of the unit through M Renewables, which is a segment of METLEN's Energy Sector. The company has proven experience in implementing complex energy storage (BESS) projects, with presence and projects on five continents.

Existing Partnership Foundation

The partnership builds on existing cooperation between the two companies in the sale and absorption of green energy. Since August 2024, this cooperation has involved the implementation of a portfolio of solar stations with a total capacity of 262MW in the same region of Thessaly. The companies have had excellent cooperation in the last few years, providing a foundation for this expanded partnership in energy storage.

METLEN's Energy Storage Portfolio

In 2024 alone, METLEN completed storage projects with a total capacity of approximately 0.7GWh. The company is currently in the final stages of agreements for third-party projects totaling 2.2GWh. The M Renewables segment has demonstrated expertise across multiple continents in energy storage project implementation, positioning the company as an experienced operator in the BESS sector.

Strategic Positioning

Through strategic partnerships such as this one with Karatzis Group, METLEN reaffirms its leading role in strengthening energy security and advancing the green transition. The company describes this initiative as building the next-generation Utility. The project represents a significant development in Greece's energy infrastructure, establishing what will be the country's largest standalone energy storage facility upon completion in 2026.

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