Recently, research on information and communications technology (ICT) has entered a new age of energism, with fast growing interests worldwide from both academia and industry in addressing various issues related to energy. This calls for a fundamental paradigm change in designing signal processing/communication systems and energy systems, which are traditionally regarded as two separate domains but now intersected, requiring for a unified study. Both challenges and opportunities arise in research along this new direction. For example, there has been an upsurge of interests in developing new signal processing techniques to optimize the energy efficiency in wireless/wired communication networks. The newly emerging communication networks comprising of devices that can be powered by harvested energy from nature and/or by dedicated wireless power transmissions have also drawn increasing attention recently. Moreover, energy related signal processing issues have now been extensively investigated for new and foreseeable applications involving big data, cloud computing, as well as mobile computing. Last but not least, innovative signal processing and communication methods, for achieving optimum energy efficiency and reliability of communication systems powered by hybrid supplies from both conventional grid and renewable energy, are currently under active exploration.