There are 49 inhabited islands in the Croatian Adriatic with a total population of 124,955 according to the 2011 census. Many studies and analyzes have shown that inhabited Croatian islands can meet all their energy needs from locally available renewable energy sources. The studies were done for the islands of Krk, Unije, Lošinj in the northern Adriatic and Mljet, Lastovo and Korčula in the southern Adriatic. The construction of smart energy systems on Croatian islands has become crucial in order to increase the penetration of renewable energy sources and local transport. All inhabited islands are connected to the national electricity system by submarine cables to the mainland. An increasing number of Croatian Adriatic islands want to be energy independent and are turning to renewable energy sources, which, when owned by citizens, have set a strong lever for local sustainable development. Croatia has great potential for the use of renewable energy sources and should encourage people to enter through energy cooperatives because it is of great importance to engage the local population to achieve the positive effects of renewable energies and for investment. The island of Krk was the first in Croatia to establish an energy cooperative with the aim of promoting the use of renewable energy sources among the local population and companies.