The chapter discusses the effects of sectoral energy efficiency on greenhouse gas emission for given levels of energy poverty and economic growth in the developing countries. As a measure of sectoral energy efficiency, a total factor energy efficiency score has been estimated across selected developing countries from Asia and Africa, for three primary economic sectors, viz., Agriculture, Industry and Services. The chapter concludes that energy efficiency has several environmental benefits; it helps to break the direct link between energy usage and GHG emissions by improving industrial efficiency, agricultural efficiency and service sector efficiency, reduced demand for energy infrastructure, and through behavioural changes. In the industrial sector, energy management systems like process optimisation, equipment upgrades, waste heat recovery and cogeneration reduce energy consumption and GHG emissions, thereby promoting efficient industrial practices. Policymakers can integrate energy efficiency into development strategies, so as to promote sustainable development, improve energy security and lower GHG emissions, by combining policy measures with financial incentives, stake-holder engagement, public awareness campaigns and capacity building. This requires collaboration between the government, international organisations and communities for a more equitable and sustainable future. Policymakers can identify successful strategies by monitoring and evaluating the effectiveness of energy efficiency measures and make informed decisions in the future. Resources should be allocated to support research and development focused on cost-effective energy efficient technologies to meet efficiency standards for industrial processes in order to support sustainable development.