Providing our society with clean and affordable energy has become one of the most important challenge of our times. In thepast few years, the use of nanomaterials for energy-relevant technologies has become a topic of rapidly increasing interest.On the one hand, this is because nanostructured matter offers a route to novel materials, tailored to exhibit specific properties.On the other hand, nanoscale systems have a huge surface-to-volume ratio - and many energy-relevant processes take place atsurfaces and interfaces (friction, charge transfer and storage, light-energy conversion, etc.). Some major challenges that need tobe overcome in order to use nanotechnology in energy-relevant technologies are the production of sufficient amounts of material,a thorough understanding of the basic properties, and the integration into technologically relevant structures. In this talk, thesetopics will be addressed in the context of a few examples, which show the potential of nanomaterials in energy technologies. Inparticular, the use of nanoparticles from the gasphase will be discussed. Select topics will include thermoelectrics, photovoltaics,solid-state lighting, and battery technologies.