Quality of Life and Energy Efficiency in Europe—A Multi-Criteria Classification of Countries and Analysis of Regional Disproportions

Energy efficiency (EE) is an important driver of quality of life (QoL), which is an overarching goal of sustainable development (SD). The levels of these phenomena in the European Union (EU) vary. Previous analyses presented in the literature have focused mainly on a one-dimensional view of EE and QoL. The authors of this article, given the multidimensional nature of the phenomena under study, present both categories from a holistic perspective. The purpose of this study was to identify the level of QoL in the context of EE and to compare the results of the classification of EU countries in terms of the analyzed phenomena. The study was conducted using the ELECTRE Tri method, one of the advanced techniques of multi-criteria decision analysis (MCDA). The classification procedure used made it possible to assign countries to predefined decision-making categories on the basis of preference threshold values and dominance relations to reference profiles. The 27 EU member states were analyzed on the basis of empirical data from 2023, using a set of 20 indicators characterizing EE and QoL. Countries were assigned to one of five classes, differentiating the level of development in both analyzed areas. Optimistic and pessimistic approaches were used to assess the stability of the classifications. The analysis showed the presence of countries with consistent results (e.g., Poland and Germany), extreme countries (Ireland and the Netherlands—high QoL with low EE; Romania and Croatia—inversely), as well as non-unique cases (e.g., Malta, the Czech Republic/Czechia, and Finland). The spatial approach indicated regions requiring special support. The results of the study can be a useful tool to support the process of designing public policies aimed at integrating social, economic, energy, and environmental goals within SD.