Multifunctional ZnO semiconductor is a potential candidate for electronics and optoelectronics applications and can be commercialized owing to its excellent electrical and optical properties, inexpensiveness, relative abundance, chemical stability towards air, and much simpler and wide range of crystal-growth technologies. The semiconducting and piezoelectric properties of environmental friendly ZnO are extremely important for energy harvesting devices. This article reviews the importance of energy harvesting using ZnO nanostructures, mainly focusing on ZnO nanostructure-based photovoltaics, piezoelectric nanogenerators, and the hybrid approach to energy harvesting. Several research and design efforts leading to commercial products in the field of energy harvesting are discussed. This paper discusses the future goals that must be achieved to commercialize these approaches for everyday use.