Nanofluids are capable of increasing the transfer of thermal energy in storage systems, especially in solar energy applications. The capacity of the system to hold energy can be improved with the application of nanoparticles in fluid systems. In the case of solar collectors, heat absorption can be maximized by taking advantage of the conductivity of the nanofluids, leading to improved energy storage capacity. Faster melting and solidification can be facilitated in the case of the material that changes phase (phase change material) with the application of nanofluids. Improved energy transfer, energy storage and reduced size of the equipment are important aspects of the application of nanofluids in the energy storage system. This chapter summarizes the research in nanofluid applications in energy storage. It also underlines the advantages and limitations of the nanofluid application in energy storage.