Long term planning for a clean energy transition in South Africa’s Electricity Sector: An integrated MAED-OSeMOSYS Approach

South Africa faces a critical challenge: meeting rapidly growing electricity demand while transitioning away from its coal-dominated power system to achieve Net Zero 2050. Although several studies have modelled South Africa's long-term electricity sector, none have applied a soft-linked demand-generation expansion planning framework and existing demand projections extending to 2050 rely on pre-COVID growth assumptions. This study addresses these gaps by developing an integrated annual-resolution MAED-OSeMOSYS framework to generate updated bottom-up electricity demand projections and evaluate least-cost electricity supply pathways from 2024 to 2050 across a baseline case and four policy-relevant scenarios. Results show that a renewables-led generation mix - reaching 75% under least-cost conditions and 94% under a Net Zero constraint - is both technically feasible and economically rational, with wind and solar PV dominating new capacity and battery storage playing an increasingly critical balancing role from 2030 onwards. The Integrated Resource Plan 2023 is broadly consistent with a least-cost transition in the near term, but its planning horizon is insufficient to deliver Net Zero 2050. Five policy recommendations are proposed, including a long-term capacity expansion plan to 2050, strengthened NDC emissions targets, and greater alignment between renewable deployment, grid expansion and international climate finance.