Energy security in the current geo-political context is an essential aspect and directs supranational strategies and policies, especially at European Union level, towards finding new sustainable solutions to restore the balance in the European energy system. We propose to analyse sustainability objectives in the energy sector through a spectral analysis of the dynamics of the main indicators over a period of 11 years, judging that this period adequately captures the causal vulnerabilities induced by economic crises and other socio-economic events, which makes renewable energy relevant as a new support for regional economic development among the European Union. The novelty of the approach lies in the assessment of renewable energy at the regional level in the context of the global economic and pandemic crises, which have been determining factors in the current geo-political and economic developments. We also aim to create energy sustainability clusters in the presence and absence of seasonality. The methods and procedures used will be represented by a critical literature review in order to verify the working hypotheses and to design, test and validate a new statistical model of energy sustainability seasonality. The modelling results will enable the creation of an EU-wide sustainability profile useful to supranational decision-makers for adjusting energy policies to ensure the energy transition towards 2050.