Piezoelectric and triboelectric nanogenerators are the two recently developed technologies for effective harvesting of ambient mechanical energy for self-powered systems. The work herein briefly reports the trends and impacts of research based on piezoelectric and triboelectric nanogenerators. For the first time, a statistical study of publication trends in piezo- and triboelectric nanogenerators is used to investigate the current state of the research. We investigate the status of the research in these fields, based on their S-shaped history, as a description of their growth in size over time, considering the number of citations and published papers that use these two novel technologies. A brief discussion of the outlook for these technologies and their potential impact on everyday life is presented, particularly in the development of future ‘smart’ cities.