Energy sector is a key player in the economic and social growth of a nation and to the quality of humans’ lifestyle. However, considering the way it is being mined, generated and employed, two serious flows have arisen. Foremost, the whole power supply system has become very ineffective. Secondly, important ecological burdens are generated from the activities linked to the power supply system. Thus, over the last decade, the sustainability assessment of electricity technologies has drawn significant attention from scholars and industrial practitioners. Decision regarding sustainable energy development is based on a wide range of indicators. However, in the context of the South African energy sector, there is a paucity of such wide analysis. Therefore, to bridge this gap, we have made use of the weighted sum method, which is one of the multi criteria decision analysis approach to assess and compare 9 different electricity generating technologies on a basis of 7 sustainability indicators (load factor, the operations and maintenance costs, the costs of producing electricity, greenhouse gases emissions, Sulphur dioxide, oxides of nitrogen; and lead. The results of the assessments demonstrate that off all technologies wind and solar thermal are the most sustainable alternatives in the context of South Africa. Additionally, we have noticed that hydropower and geothermal technologies have the potential to provide considerable sustainability developments over conventional power technologies (coal, gas, and nuclear). Lastly, off conventional technologies coal and gas demonstrate a good sustainability performance than coal in most cases.