The global energy landscape has changed significantly in recent years and the transition to a decarbonised energy system is well underway. Transparent, flexible and integrated energy systems models are essential tools for providing credible evidence-based knowledge for future energy infrastructure planning. This report outlines the most important aspects needed to be considered in the energy modelling processes used to inform future energy investment pathways of South Africa, while meeting national carbon emission commitments and socio-economic development priorities. The costs of energy technologies especially solar, wind and battery storage have dropped significantly in recent times and have now become cost competitive with conventional fossil fuel alternatives. This has created an opportunity to rapidly transition to a low-carbon global energy system without significant economic compromises as previously expected. However, the structural changes of energy systems resulting from the incorporation of large amounts of non-dispatchable renewable power generation into the electricity system brings new challenges and potentially far reaching implications. Understanding the complex interactions of the numerous interconnected factors involved, and the implications of various planning choices for the environment and national objectives are essential to prepare adequate national transition plans, road maps and policies. This requires a detailed understanding of available renewable resources, especially solar and wind; the flexibility requirements of the overall system; the projections for likely demand growth trajectories; and global commodity and fuel price uncertainties. The opportunities for energy storage to allow for improved coordination between supply and demand are considerable with electro-chemical storage (batteries) and resulting controllable demand-resources in the electricity sector specifically being notable examples.