Non-Interconnected Islands (NIIs) are the islands of the Greek territory whose Electricity Distribution Network is not connected to the Transmission System or the Distribution Network of the mainland. The operation of the Electric Systems of the NIIs, which includes the production management, the operation of the market and systems of these islands, is the responsibility of DEDDIE S.A. and is carried out according to the “Non-Interconnected Islands Electricity System Operation Code”, provided for in article 130 of Law 4001/2011.

With the completion of Phase 1 of the Cyclades interconnection (Syros, Mykonos, Paros and Naxos) with the Continental System in March 2018, the method of electrification of the NIIs of the country has changed a lot. With the completion of the 2nd and 3rd Phases of the Cyclades interconnection, the reliability of their electricity supply will be further guaranteed. However, a significant number of NIIs continue to be electrified by the local PPC S.A. production stations, which operate with oil or even diesel. The contribution of RES, especially the wind and PV plants, which operate on these islands, is also important.

The electricity market of the Non-Interconnected Islands consists of twenty-nine (29) autonomous systems. Some of them consist of several islands (island complexes). The size of the country’s twenty-nine (29) autonomous island power systems varies:

Nineteen (19) “small” stand-alone systems with a peak demand of up to 10 MW.
Eight (8) “medium-sized” stand-alone systems with peak demand from 10 MW to 100 MW.
Two (2) “large” autonomous systems with a peak demand of more than 100 MW (Crete and Rhodes).
The annual electricity demand in the NIIs varies in size, from several hundreds of MWh in the smallest islands (e.g. Antikythera, Agathonissi, etc.), to several TWh in the largest NII (Crete).