Agios Efstratios, the small northern Aegean island also known as Ai Stratis, has become one of Greece’s most important pilot cases for the clean energy transition, after renewable energy sources covered up to 98% of the island’s monthly electricity needs during the spring of 2026.

The results of the Special Pilot Project “Ai Stratis – Green Island” confirm the success of one of the most innovative energy-transition projects yet implemented on Greece’s Non-Interconnected Islands, meaning islands that are not linked to the mainland electricity grid.

During March, April and May 2026, renewable energy penetration in the sustainable island’s power system reached as high as 98% on a monthly basis. This significantly reduced the use and cost of the conventional thermal power plant, while also cutting the island’s environmental footprint.

The project is seen as a model for how Greek islands can move towards a cleaner and more sustainable energy system. It combines electricity generation from renewable energy sources with electrical and thermal energy storage, allowing most of the island’s needs to be covered by clean energy.

The Hybrid Power Plant includes a wind turbine, a photovoltaic station and battery storage. The project also includes a district heating system that stores thermal energy in water tanks, creating an integrated energy system designed to maximise the use of renewable sources.

The project was implemented by CRES, Greece’s Centre for Renewable Energy Sources and Saving, on behalf of the Municipality of Agios Efstratios, with funding from the NSRF, Greece’s National Strategic Reference Framework.

A decisive role was also played by HEDNO, the Hellenic Electricity Distribution Network Operator, which operates Greece’s Non-Interconnected Islands. HEDNO designed and implemented advanced automated procedures and innovative algorithms to manage the Agios Efstratios power system, ensuring reliable and safe operation under all conditions, as well as a smooth transition between the conventional thermal plant and the Hybrid Power Station.

The system operates through a fully automated Dispatch Programme, developed specifically for the project. Every 20 minutes, it calculates and applies the optimal use of the available generation units, based on energy demand and prevailing conditions.

To support the project’s successful operation, HEDNO carried out major upgrades to the island’s monitoring and control systems, known as SCADA-EMS. It also developed new operating procedures and algorithms, conducted extensive testing, and ensured continuous monitoring and optimisation of the island’s power system.

Operational testing of the Hybrid Station began in July 2025, while full-scale operation started in November of the same year.

The expertise gained by HEDNO through the Agios Efstratios project is expected to support the development of similar high-renewable energy projects and hybrid power plants on other Non-Interconnected Islands, accelerating the energy transition and strengthening sustainable development across island Greece.

The Agios Efstratios project shows in practice that, with innovative technologies, advanced management systems and specialised technical expertise, Greek islands can move towards a more modern, reliable and environmentally friendly energy future.

Read more about ecologically sustainable Greek islands