Energy planning refers to providing sufficient power to human societies while at the same time underlies resource, economic environmental, social and technological constraints. The complexity of the task renders multi-criteria decision analysis techniques a useful tool in the decision process. Multi-criteria decision analysis techniques offer a transparent way of elaborating on decision problems, which include many criteria and different decision-makers. This article presents the MCDA-RES multi-criteria decision-analysis software and its application in a case-study regarding a wind-hydro hybrid energy project for an island in Greece where the performance of alternatives on a set of different criteria and the preference of the decision-makers is assessed. The analysis showed that no group consensus could be directly established; still some alternatives performed better than others and a way towards a compromise solution could be revealed.