Nanophotonics is an emerging field with significant potential for generating energy-efficient technology. Specifically, photonic crystal technology possesses unique optical properties that enable light manipulation at the nanoscale, leading to advancements in energy applications such as photovoltaics, light-emitting diodes, solid-state lighting, solar cells, and energy harvesting. This chapter provides a comprehensive examination of nanophotonics technology for energy applications, including energy harvesting, LED lighting, and energy storage devices, such as Filters in Thermophotovoltaic Systems and Photonic-Crystal-Based Daytime Passive Radiative Coolers. Moreover, the current chapter offers a comprehensive review of current breakthroughs, challenges, opportunities, and prospects in the field of nanophotonic crystals for energy applications. This chapter serves as a valuable resource for academics and engineers interested in developing and implementing nanophotonic crystal technology for energy applications. Finally, the chapter explores prospects of development of energy-efficient technologies.