In recent years, the number of connected devices and systems has increased ex- ponentially, along with their use in our daily life. Cyber-Physical Systems (CPS) are complex multi-layered feedback systems that combine computing resources and interaction with the physical environment using sensors and actuators. Energy is considered one of the major concerns driven by the increasing number of connected devices and systems. In this paper, we review current research approaches and di- rections in energy-aware CPS. We propose a novel architectural methodology to analyze and compare state-of-the-art approaches, on their architectural design and energy-related factors. We finally draw recommendations from our review on how to build energy-aware and energy-efficient CPS solutions.