As a building element, the facade which interacts with external factors between two different environmental conditions is an important interface in energy consumption and the building life cycle. In recent years, smart materials have become a research topic in the field of sustainable architecture and facade technologies. The traditional material understanding which expects materials to not be affected by external environmental conditions by preserving their qualities throughout their lifespan has begun to leave its place to the understanding of materials that change quality and energy by reacting to external stimuli. Developing facade technologies and the energy-efficient design approach also achieve the development of new technologies in window systems. The most promising of these new window technologies, called smart windows, are electrochromic, thermochromic, and photochromic windows. Within the scope of this study, the energy performance of smart window systems has been evaluated comparatively with a traditional window system in a reference office building in Kayseri, Turkey. This study aims to evaluate the energy performances of smart windows and reveal their advantages and disadvantages over the available window system in this climate condition. In this context, smart window systems have been classified and explained their properties. In the simulation part, a reference office building has been modeled with each smart window system to evaluate their energy performances comparatively. Nevertheless, a reference office building with a traditional window system has also been modeled to reveal differences in energy performances with an available window system. Finally, the results have been evaluated with graphs and recommendations on the best-performed window system have been explained.