This study examines the combination of renewable energy sources for electricity generation at local level, and in particular the case of an isolated area of South Crete, the Frangocastello area, with the help of F-Cast, a computerized model that has been developed for the simulation of the operation of an integrated system, The energy supply side includes three renewable energy sources, namely wind, micro-hydraulic and biomass, and conventional high-cost electricity supplied by the National Grid, The model is the economic counterpart of an electronic control system that dispatches electricity on an hourly basis, Wind energy introduces uncertainty to the system, Relations among variables are based on three states of the world depending upon the hourly speed of the wind, Biomass is a balancing factor in the supply-demand interaction, as the production of biomass is itself at the same time consuming electricity, as an input, Conclusions are drawn on (a) the optimal combination of renewable energy sources to achieve economic viability of the system (b) effects on agricultural income and local development, and (c) evaluation of renewable energy policies.