The resource base for RES is vast, but only a small fraction is being exploited with available technology. The full potential of RES for the European Union (EU) is estimated at 408 Mtoe by 2020. Here, we review data on energy supplies and demand with emphasis on RES and also assess the potential for energy conservation by using RES in remote regions. Our case study deals with the Hellenic islands of the North Aegean region. These islands have a high RES potential because of their dependence on external energy sources, absence of control over fossil-fuel costs and periodic power shortages, especially during summers when energy demands peak as a result of tourism.