Over the past 10 years, the development of renewable and green energy technologies has significantly accelerated due to the world’s rising energy demand and environmental pollution from conventional sources. In this regard, the potential of newly created nanocomposites with distinctive properties in a variety of energy-related applications has been demonstrated. In order to provide uninterrupted power supplies, energy sector products like solar cells, rechargeable batteries, fuel cells, and supercapacitors are crucial in today’s modern society. Electrolytes and electrode materials based on nanofillers have been established to eradicate the problems with conventional batteries and to enhance the performance of supercapacitors through ionic conductivity. It is important to note that improved energy-yielding components were produced as a result of the excellent physicochemical properties of carbon and polymer-based nanofillers. The thermal, mechanical, optical, and electrical properties of these nanofillers were found to be good, whereas they were lacking in earlier materials. Nanoparticles have been added as nanofillers to these composites in order to create reinforced materials and new materials with unique properties. The improvement in high ionic conductivity and stability was the most notable benefit of nanofillers-based electrolytes or electrodes. This chapter was written so that readers would understand how recently formed nanofillers have been used in the energy sector.