A small Greek island in the northeastern Aegean is showing how renewable energy can transform how remote communities generate electricity and heat their homes.
Agios Efstratios, also known as Ai Stratis, has developed a hybrid energy system combining wind power, solar energy, battery storage, and district heating to reduce its dependence on fossil fuels.
Home to approximately 250 residents, the volcanic island was historically reliant on conventional fuel for electricity generation. Its geographical isolation made energy security a particular challenge, leaving the community exposed to fuel costs and the logistical difficulties of supplying a remote island.
The EU-supported Ai Stratis Green Island project was designed to address those challenges by integrating several technologies into one system.
According to recent reporting, renewable sources now account for around 91% of the island’s electricity generation. The project is also designed to reduce carbon emissions by approximately 1,000 tonnes annually.
Rather than relying on a single source of renewable power, the system combines electricity generation, storage and heating to make better use of the island’s available energy resources.
A hybrid system combining wind, solar and battery storage
The island’s renewable energy infrastructure centres on a 900-kilowatt wind turbine and a solar photovoltaic installation with a capacity of approximately 226.8 kilowatt-peak.
A lithium-ion battery system with a storage capacity of 2.56 megawatt-hours helps balance electricity supply and demand.
The batteries store surplus electricity when renewable generation exceeds demand and release it when production falls. An automated energy management system coordinates the different components, helping maintain a stable supply across the island’s local electricity network.
Aigos Efstratios, at the forefront of Greece's energy transition
— Aurora Velez (@goizlyon) October 2, 2026
Zoi Vlastou, Deputy Major for Citizen Services stresses emphasizes the importance of "Ai Stratis -Green Island" pilot project, as a model for the rest of Greece pic.twitter.com/HlN95ie1AT
The system is particularly important because Agios Efstratios is not connected to the mainland electricity grid.
Its energy infrastructure must therefore manage fluctuations in wind and solar production locally, rather than relying on electricity imports from a larger interconnected network.
The project aims to cover the island’s electricity needs through renewable generation for much of the year, while substantially reducing the role of conventional fuel.
The distinction matters: the reported figure of approximately 91% refers to renewable electricity generation, not a guarantee that every unit of energy consumed on the island comes from renewable sources at all times.
Surplus electricity is also used to heat homes
One of the project’s most distinctive features is its integration of electricity generation with district heating.
When wind and solar production exceeds immediate electricity demand, the surplus can be used to heat water. The thermal energy is then stored for later use, particularly during the colder months when household heating requirements increase.
The system includes four hot water storage tanks with a combined capacity of approximately 500 cubic metres.
Stored heat is distributed through a district heating network, reducing the need for individual households to rely on conventional oil-fired boilers.
This approach allows the island to use renewable electricity productively that might otherwise exceed immediate demand.
It also demonstrates how energy storage can extend beyond batteries. Electrical storage helps balance the power network, while thermal storage provides another way to retain surplus energy for use when it is needed.
For residents, the change can mean quieter heating systems and less reliance on fuel deliveries.
Charalambos Makris, a local resident who manages two guesthouses, described the benefits of the new heating arrangements, saying there was no longer a need to operate a boiler inside the house.
He also highlighted the reduced noise and the system’s economical operation.
From pilot project to operational energy infrastructure
The project has progressed considerably since its initial development.
Trial operation began in July 2025, and the official project website reports that the hybrid power station was commissioned in November 2025 after testing and approval by Greece’s electricity distribution operator.
The heating system also began operating in late 2025, according to the project information.
The transition from construction to operation is significant because renewable energy projects on isolated islands face challenges that extend beyond installing turbines and solar panels.
They must maintain a reliable electricity supply despite changes in weather, seasonal demand and renewable generation. Battery storage, automated controls, and supplementary conventional equipment can all help keep the system operational.
The project retains an auxiliary conventional fuel boiler for periods when renewable energy and stored heat are insufficient.
Agios Efstratios is therefore better understood as a major step towards energy independence than as an island that has completely eliminated fossil fuels.
A €7.23 million project backed by European funding
The newer report puts the project’s budget at €7.23 million, with 85% funded through the European Union’s Cohesion Policy and the remaining 15% provided by Greek national funds.
The official project website also lists an approved budget of €8.5 million, including VAT, across two project phases. The figures may reflect different funding scopes or accounting bases and should not be treated as directly equivalent without further clarification.
The project required substantial engineering and logistical work.
Among the challenges was transporting and installing the island’s wind turbine, which stands approximately 77 metres tall and weighs close to 30 tonnes.
The team also faced regulatory hurdles because Greece’s existing energy framework was not specifically designed for a remote electricity system integrating renewable generation, battery storage, automated controls and district heating.
Manolis Klados, a project manager at GEK TERNA Group, has described how surplus electricity is stored in batteries and released when renewable production falls. In winter, additional surplus can be converted into heat and stored in the hot water tanks.
The project has brought together public funding, technical expertise and local infrastructure to demonstrate how an isolated island can make greater use of its own renewable resources.
Could other Greek islands follow its example?
Agios Efstratios forms part of a broader effort to improve energy security and expand renewable energy across Greece’s islands.
Tilos, Ikaria and Astypalea have also pursued renewable energy initiatives, although their technologies, objectives and levels of energy independence differ.
Many Greek islands face similar challenges, including dependence on imported fuel, isolated electricity networks and substantial seasonal fluctuations in demand.
Renewable energy can help address those pressures, but each island requires a system suited to its population, geography, weather conditions and energy consumption.
Agios Efstratios offers an example of how wind power, solar generation, battery storage and district heating can operate as parts of a coordinated energy network.
Its experience could help inform future projects in Greece and elsewhere in Europe, particularly in remote communities seeking to reduce emissions and become less vulnerable to international fuel price fluctuations.
For a small island in the Aegean, the project represents more than installing renewable energy equipment. It is an effort to reshape how electricity and heat are produced, stored and delivered to residents.
The ultimate measure of its success will be the system’s long-term reliability, its contribution to lower emissions and the savings it can deliver to the community.
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