This study investigates barriers to effective energy management in existing buildings within Johannesburg, South Africa, in the context of Sustainable Development Goal 7 (SDG 7). Despite policy commitments and growing awareness, energy-efficiency implementation in existing buildings remains limited, indicating a gap between policy intent and practical execution. The study adopts a quantitative research approach, using a structured questionnaire distributed to construction professionals at 10 selected companies. Data were analyzed using Mean Item Score (MIS) and standard deviation to identify and rank key barriers. The findings reveal that inadequate investment in clean energy, continued reliance on fossil fuels, and high energy costs are the most critical constraints affecting energy management in buildings. Additional barriers include regulatory inefficiencies, skills shortages, and low stakeholder awareness. The consistency of responses suggests systemic challenges rather than isolated issues. The study contributes by reframing SDG 7 implementation challenges as an energy management problem and provides context-specific insights for developing economies. The paper recommends strengthening financial mechanisms, improving regulatory enforcement, enhancing technical capacity, and promoting Public-Private Partnerships (PPPs) to improve energy management practices. These interventions are essential to bridge the gap between sustainability policy and real-world implementation in the built environment.