This thesis develops a comprehensive macroeconomic-energy model to determine two scenarios from Portugal by 2050: a Business-as-Usual and an Optimistic one aligned with the national climate roadmap RNC2050. It unifies socioeconomic drivers, such as human labour and capital, with energy system processes, using an exergy-based methodology that allows calculation of Total Factor Productivity and carbon emissions as endogenous outcomes. Through the integration of sectoral investments, renewable energy cost projections and end-use final exergy distribution by sectors, carriers and end-uses, the model estimates CO₂ emissions and carbon intensity for both scenarios. Outcomes show that although both scenarios predict decreasing emissions, however only the Optimistic Scenario comes approaches carbon neutrality, driven by widespread electrification, large-scale adoption of renewables and structural transformation of the economy.