Smart grid technologies can be defined as self-sufficient systems that can find solutions to problems quickly in an available system that reduces the workforce and targets sustainable, reliable, safe and quality electricity to all consumers. In this respect, different technological applications can be seen from the perspective of researchers and investors. Even though these technological application studies constitute an initial step for the structure of the smart grid, they have not been fully completed in many countries. Associations of initial studies for the next step in smart grid applications will provide an economic benefit for the authorities in the long term, and will help to establish standards to be compatible with every application so that all smart grid applications can be coordinated under the control of the same authorities. In this study, a review has been made of technological methods of data transmission and the energy efficiency in smart grids as well as smart grid applications. Therefore, this study is expected to be an important guiding source for researchers and engineers studying the smart grid. It also helps transmission and distribution system operators to follow the right path as they are transforming their classical grids to smart grids. ; JRC.C.3-Energy Security, Distribution and Markets