Recently, an improvement of the United Nations Human Development Index (HDI), named the Thermodynamic Human Development Index (THDI), has been introduced to link socio-economics to environmental and technical pillars of sustainable development. In this paper, the THDI is linked to the Kaya identity to bring out the quantities useful in energy economics and to obtain a clearer tool for the evaluation of sustainability. Moreover, the THDI has been normalized for use as an index for the analysis of sustainability. The component related to environmental emissions, which is included in the THDI, can be linked to the Kaya identity. This linkage allows us to use the THDI for the analysis of scenarios, which is useful for evaluating the possible impacts of any future actions on the development of countries.