doi:10.1007/s13762-026-07161-wengCarvalho, M.de Mello Delgado, D. B.Abrahão, R.Guillén-Lambea, S.Rethinking environmental payback: its declining relevance in the decarbonization of the electricity mixART-2026-148966This study identifies, discusses and analyzes the most commonly used parameters for the evaluation of energy systems from an environmental perspective. This work provides a critical assessment of the applicability of environmental payback time as a metric for evaluating energy systems, particularly in the context of ongoing decarbonization efforts. A new environmental indicator is proposed, the dynamic payback time, which incorporates the evolution of the emission factor for the electricity grid throughout the operational lifetime of the energy system. The results of two case studies in two countries with dissimilar energy structures and diverse development of electricity generation systems (Brazil and Spain) are presented. A new parameter is presented, the EME parameter (Embodied emissions divided by the electricity Mix Emissions), which can help determine the potential impact of an energy system in the overall energy mix of a country. The results confirm that temporal evolution is a crucial parameter in the environmental assessment of energy systems, concluding that new dynamic parameters are essential for consolidating the findings from environmental studies.2026http://zaguan.unizar.es/record/17047010.1007/s13762-026-07161-whttp://zaguan.unizar.es/record/170470oai:zaguan.unizar.es:170470info:eu-repo/grantAgreement/ES/MCIN/RYC2021-034265-IINTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY 23, 5 (2026), [13 pp.]byhttps://creativecommons.org/licenses/by/4.0/deed.esinfo:eu-repo/semantics/openAccess