The twelve articles in this special section focus on energy efficiency as it relates to fog or edge computing. The Internet of Things (IoT) has emerged as one of the most advanced and complex technological trends, where more than 50 billion things will be connected (e.g., mobile devices, sensors, wearable devices, and other computing nodes) to the Internet by 2020. Edge/fog computing will play an increasingly important role in handling the information flow of such large and complex networks. An unintended consequence is the impact of their operations on carbon emissions and the resulting electricity costs. Thus, there has been focus on designing energy-efficient solutions for the edge-fog environment. In this Feature Topic, state-of-the-art research advances in energy efficiency and sustainability for edge/fog deployment are presented.