Multicriteria decision-making theory has been widely used for sustainability assessment in the context of energy management. Although it is not a simple task, requirements are available in the literature to guide analysts performing this type of assessments. When it comes to emerging technologies, specific conditions such unknown impacts, lack of data, high uncertainty, etc., can increase the complexity of the task. Here we present an overview of the concepts of MCDA sustainability assessment, examples of existing studies in the field of energy storage, and a use case for the sustainability assessment of early-stage cathode materials for sodium ion batteries using PROMETHEE II. The results in this type of assessment serve as an indicative for further research and development of specific technologies/materials. Factors such as the availability of data and dynamic social contexts (e.g., political priorities) make sustainability assessments an iterative process. Systematic approaches and specialized MCDA software are necessary to support this task.