In this study, smart energy systems are investigated and comparatively assessed to solve major global energy-related issues in a sustainable manner. In order to be considered as smart and sustainable, the energy systems should use technologies and resources that are adequate, affordable, clean, and reliable. Therefore, selected smart energy systems are evaluated based on their efficiencies, environmental performance, and energy and material sources. Our results show that increasing the number of products from the same energy source decreases emissions per unit product and increases efficiencies. Also, among the identified sources, geothermal has the most potential in terms of using cleaner technologies with energy conservation, renewability and the possibility of multiple desired products from the same source. Solar, hydro, and biomass are also beneficial. Even with carbon capture technologies, fossil fuels are not very desirable in smart energy systems because of their emissions and non-renewability. (C) 2016 Elsevier Ltd. All rights reserved.