Towards decarbonisation of geographical islands in the Mediterranean, PRISMI proposes the use of a methodology toolkit which includes a Load-Flow (LF) analysis tool. This tool is used to assess the impact of selected RES in island grids. The proposed tool is advantageous because it combines useful features in a simple and straightforward way. Its minimal requirements in terms of input parameters make it userfriendly and provide a quick assessment of RES scenarios impact. To this purpose, the proposed tool is offered as a stand-alone application, and uses grid, and power data from previous steps of the methodology to calculate the grid voltages and currents. The tool is equipped with an interface that allows selection of test grids among preset or custom models, specification of the timeframes for the LF calculation, simplified drawing of the grid, and modifiable operating voltage and capacity limits. The tool also provides information about the voltage and capacity limits violations as well as a graphical illustration of all the problematic and normal parts of the grid. In the specific work the basic features of the proposed tool are presented together with the implementation results for two selected reference power systems. (C) 2019 Elsevier Ltd. All rights reserved.