In this work authors are analyzing mobile ad-hoc networks (MANET) and cognitive radio ad-hoc networks (CRAHN) solutions from routing protocols point of view, in order to identify promising directions of the future research, which could be developed towards energy efficient routing protocols for future cellular networks. Literature studies are covering cognitive solutions implementation in cellular environment. Standardization developments were studied, in order to identify industry's views on the energy efficiency aspects in networks, as well as on the alternative offloading solutions. Based on the compilation of the research and industry overviews, various deployment scenarios are considered, including inter-UE, intra-operator, as well as inter-operator case. Number of concepts was identified, including radio resource management solutions, proposals related to the introduction of energy efficiency related performance indicators in networks, or cooperative schemes in inter-operator networks, which could be studied from the energy efficiency point of view. Proposed ideas are basis for further research work.