The emergence of mobile cloud computing (MCC) indicates that increasingly abundant applications are available, thus deeming energy problems even more significant. To achieve energy optimization in mobile systems, power consumption involved with each component or application need to be estimated prior to execution. In this paper, we present a survey on the universal energy estimation model for mobile devices. Additionally, due to the significance of wireless network interface card (WNIC) in the power use of mobile devices, considerable researches have been devoted to a low-power design of the WNIC (i.e., Cellular and WiFi). These efforts have allowed us to provide a comprehensive summary of recent work on transmission energy savings. Finally, we conclude the survey and discuss the future research directions.