Water supply is of great importance for the sustainability of urban areas. It is a known fact that increasing amounts of energy from fossil fuelsare used for this purpose, whose price is daily increasing. The use of Renewable Energy Sources (RES), in particular solar Photovoltaic (PV) energy is an alternative solutionto this problem. This thesis on innovative and original way proves the sustainability of Urban Water Supply System (UWSS), by using PV energy. Concept of using the PV energy in UWSS in this thesis is based on a method called Critical Period Method (CPM). Within CPM, critical periods and balancing periods were defined. By their introduction and application, respectively by use of the CPM, sustainability of the obtained solutionis achieved, to give the Energy Sustainable Urban Water Supply System (ESUWSS). In this thesis, hydraulically and energetically features, and also a sizing methodology of ESUWSS have been shown on a hypothetical example that has the characteristics of a real analyzed problem. The obtained results confirmed the hypothesis that PV energy is suitable for use in UWSS, i.e. for driving (electric) energy of pumping stations. The obtained solution is hydraulically and energetically sustainable. In the proposed solution, water reservoir (with the usual role of water storage) has the role of energy storage. The presented solution has a positive impact on the climate changes, since it significantly contributes to the reduction of greenhouse gas emissions. Herein, classical electric energy, produced by the use of fossil fuels, is entirely replaced with ''green'' energy from the PV system. Thereby, the amounts of greenhouse gases that are released are insignificant. The proposed solution has a positive social impact on wider and narrower community, since ESUWSS provides social benefits in all its aspects. The presented solution, as well as sizing methodology of ESUWSS, is widely applicable to various characteristics of a water supply system and climate.