Nonrenewable sources of energy have been rapidly growing in recent years and research emphasis has been directed to the utilization of renewable energy sources for a cleaner and healthier environment. For over two decades, researchers have investigated many possibilities in terms of renewable energies to generate sustainable energy. Solar cells, fuel cells, photoelectrolysis, supercapacitors, batteries, and wind turbines have the potential to be efficient methods to directly convert one state of energy into another one. In these new energy systems, various types of nanotechnology and their products have been utilized to increase the efficiencies of these energy systems. However, these new developments also bring many uncertainties and risks to human health and the environment. Therefore, the future of nanotechnology depends mainly on public acceptance of the risks associated with the use of nanomaterials and their benefits. Risk assessment of nanomaterials is mainly the basis of formulating guidelines of protecting human health and the environment. This chapter provides information on the current state of nanomaterials used by the energy industry and offers suggestions for continuing our path toward sustainable development in the energy field.