Building energy systems provides the support needed for the management of a building’ energy needs. These systems include artificial lighting of interiors, ventilation, air-conditioning, and refrigeration systems as well as heating systems such as hot water supply. These systems account for a large portion of a building’s operational energy use, and therefore, their decarbonization is critical in achieving carbon neutrality for buildings. Most energy systems in Africa relies heavily on non-renewable energy sources including fossil fuels and coals. Moreover, it is uncommon to find systems manufactured in Africa or with the African climate in mind. As such it is common to find some systems being highly efficient in certain climates but not as efficient within the African region. Africa continues to urbanize quickly and the use of energy systems becomes more critical. In this chapter, the various building energy systems are highlighted and key barriers to decarbonization of building energy systems are discussed. The chapter continues with opportunities in using these systems. Lastly, pathways for decarbonization of building energy-efficient systems are discussed.