Global warming and climate changes, as well as the contribution of fossil fuel to the accentuation of these phenomena are realities almost unanimously accepted. Therefore, the reduction of the coal ratio in the energy mix and its replacement with forms of energy without emissions is being discussed more and more frequently. Nevertheless, it is important that the impact generated in the environment by the alternative energy sources related to energy production does not exceed the shortcomings created by the steam power plants, as it seems to be the case of micro hydropower plants (MHC) located on the superior flow of mountain rivers. As it is difficult to compare the impact on the environment generated by two completely different energy sources, two indictors were defined and used in this sense that consider their ecological, economic and social performance. As a result of the evaluation of the impact and of the comparison criteria, the two indicators were used in the two chosen case studies, resulting that a steam power plant that operates in cogeneration has a superior eco-energy efficiency to a micro hydropower plant. Thus, following the carried-out studies, we believe that MHC can be recommended only under special circumstances such as providing electric power to areas difficult to reach without them injecting the produced energy into the National Energy System (SEN).