Abstract Every planning activity generally requires to make some choices. After a preliminary analysis of the sector under examination, a forecast of trends of input–output items, the planner must define an action plan voted to arrange all the strategies and specific interventions able to fit demand and supply during the planned time. The redaction of an action plan implies a strong effort in order to synthesize either suggestions coming from the analysis phases either all the constraints linked to technical choices. In the same time, a large number of “external” variables plays a role in orienting decision making. Some of these can be handled by numerical models (economic cost-benefit analyses, market penetration strategies, environmental impacts). Other aspects, concerning social and cultural impact, political drawbacks, aesthetic aspects, etc., can be analysed only in a qualitative way, or are subjected to a not-objective judgement. This paper aims of introducing a methodological tool able to “organize” and “synthesize” the large set of variables coming from several specific judgements (or assessments) helping the “decision maker” to read the complex problem, understand it and make choices. Previous works of the authors have presented possible applications of “multicriteria-analysis”. In particular, the ELECTRE methods family, (Roy, B., Me thodologie multicrite re d'aide a la de cision, Economica, coll. ``Gestion'', Paris, 1985) will be presented under the point of view of energy planning application. It consists in a “flexible” ranking method which takes into account the uncertainties of all the specific assessments, the qualitative nature of some indexes, the weight of the preferences or willingness systems of the decision maker. On the other hand, similar results can be obtained through the application of fuzzy sets theory (Zimmermann, H. J., Fuzzy set Theory and its Application. Kluver Academic Publisher, 1987). A decision making support method, based on fuzzy logic is here tested and compared to the previous one. A case study developed by authors will show differences among these two different approachs. It is focused on the development of a renewable energy diffusion strategies plan. Advantages and drawbacks of both methods will be explored and some suggestions will be proposed.