Energy storage is recognized as an increasingly important parameter in the electricity and energy systems, allowing the generation flexibility and therefore the demand side management. It can contribute to optimal use of generation and grid assets, and support emissions reductions in various economic sectors. Energy storage can support the European Union (EU) targets for efficient use of energy by helping to ensure energy security, a well-functioning internal energy market, and successful implementation of more carbon-cutting renewables online. By strengthen the use of energy storage, the EU can decrease its energy imports, improve the efficiency of the energy system, and keep prices low by better integrating variable renewable energy sources. Moreover energy storage can contribute to better use of renewable energy sources in the energy system since it can store energy produced when the conditions for renewable energy are appropriate but demand may be low. In this framework, primary objective of this study is the investigation, the comparative analysis and the evaluation according to specific criteria of the current thermal energy storage systems. Electrical, electrochemical, thermal, mechanical and chemical energy storage technology and systems are extensively presented and categorized in terms of their advantages and disadvantages as well as in terms of their technical and financial characteristics. This paper also presents the implementation of thermal energy storage in the residential sector. More specifically is examining the application of a phase change material storage system into the building's walls cavity. The study focuses on the contribution of the applied energy storage system to the overall increase of the energy efficiency of the building.