An important challenge for future energy systems is a new modeling methodology that integrates the cyber and physical components. This model must include the impact of communication networks and further cyber components, besides the relevant information of the physical system, in terms of efficiency, sustainability, reliability, security, and stability. The Cyber Physical Energy Systems (CPES) concept is presented as an interesting alternative to address this issue and its main features are identified. The main CPES research areas are identified as: modelling energy systems, energy efficiency, energy resource management, and energy control. In this work, the advantages of the CPES approach are shown in order to address current challenges in future energy systems. Smart grids, based on microgrids and distributed generation concepts, are identified as an interesting application of the CPES. A new proposal for modeling smart grids based on the CPES approach is introduced.