Comparative assessment of energy-related environmental impact management systems and decarbonisation policies in energy transitions

This study presents a comparative assessment of energy sustainability potential using the Integral Sustainability Potential Index (ISPI), which integrates four indicators: energy intensity (EI), the share of renewable energy sources (RES) in electricity generation, the diffusion of ISO 50001-certified energy management systems (EnMS), and political readiness. The methodology is applied to Central and Eastern European countries (Poland, Romania, Bulgaria, Slovakia, and Ukraine). The results reveal substantial cross-country differences in sustainability potential, primarily driven by institutional capacity, policy coherence, and the scale of ISO 50001 implementation. Poland demonstrated the highest ISPI value (0.68), reflecting moderate EI, a relatively high RES share, widespread adoption of ISO 50001 in the industry, and strong political support for EnMS. Romania (ISPI = 0.56), Bulgaria (ISPI = 0.39), and Slovakia (ISPI = 0.37) exhibit a medium level of sustainability potential, supported by notable RES penetration and policy initiatives but constrained by the limited diffusion of ISO 50001. Ukraine shows a significantly lower ISPI value (0.32), which is associated with high-EI (≈ 2.68 toe/1000 €), a lower RES share, weak implementation of ISO 50001, and insufficient policy support for EnMS. Cross-country analysis reveals a consistent pattern: countries with the lowest ISPI values (0.32–0.37) have the highest EI (>95 kilogrammes of oil equivalent/1000 €) and the lowest ISO 50001 certification density (