Energy issue stays a top priority for the national security of most countries. Despite numerous international forums, large-scale geoeconomic research, international and national projects, and the development of appropriate strategies, the issue of energy security assessment and understanding of its terminology is not a universal practice. The presented study has an ambitious goal to develop a methodology that can provide an objective picture of the energy sector on an international scale with cross-country comparisons under the influence of modern megatrends. Based on 29 indicators, according to the World Bank data since 1991, the energy security index is calculated for the set of world states with further analysis of the cluster dynamics of their common trends in energy security. The index showed its objectivity and resistance to existing shocks in geoeconomic dynamics. An important feature of the proposed index is the possibility to compare the energy security index with 1. This value is, in fact, a European average: if a country has an energy security index greater than 1, it means that its energy level is currently better than the European average, and if it is lower than 1, it means that it is inferior to the level of energy security currently achieved on average in Europe. The concept of calculating the index of energy security of the state is based on a unified comparison of all countries, which allows us to move away from the use of signaling approaches and eliminate subjectivity in calculations, as well as provide a basis for dynamic comparison of energy security. The vital aspect of the index is that it takes into account changes in the energy paradigm, the transition to alternative energy sources, and the comprehension of the role of energy efficiency, in particular, of fossil fuels. The study identifies clusters of countries that have consistent similarities in energy security, which can usually be of practical interest in developing energy strategies and understanding the similarity of geoeconomic interests of these states. Thus, this article contributes not only to the development of scientific approaches to the assessment of energy issues, in particular, through the methodological development of a representative index, but also through the presentation of statistically sound results for further effective management decisions at the state level.