The Energy Performance of Buildings Directive (EPBD) is a significant regulatory framework within the European Union (EU) designed to advance the efficiency and decarbonization of buildings by 2050. Since their inception in 2010 and 2023, the EPBD and the Energy Efficiency Directive (EED) have been subject to multiple amendments to improve building energy efficiency, decrease energy usage, and lower greenhouse gas emissions. An essential element of the EPBD is the energy performance certificate (EPC), which furnishes details regarding a building’s energy consumption and effectiveness. However, the conventional EPC has faced criticism for its standardized nature and lack of sufficient user-centric data. In response, the smart energy performance assessment platform (SEPAP) has been created, incorporating three distinct assessment approaches that integrate smart energy management tools, simplified monthly computations, and advanced hourly simulations. Furthermore, the EPBD has introduced the smart readiness indicator (SRI) concept, evaluating a building’s ability to adjust to occupants’ and grid requirements while enhancing energy efficiency. The SRI calculation considers the effectiveness of diverse smart-ready services in the building, with a higher rating signifying increased “smart” capabilities. The modifications made to the EPBD along with the implementation of novel resources such as SEPAP and SRI are intended to furnish building proprietors, residents, and financiers with enhanced and easily accessible details, enabling them to make knowledgeable choices regarding energy efficiency and sustainability within constructed surroundings. SRI also helps investors and customers have good information about building smartness because of building energy consumption, so this SRI can help EPC investigate EPBD goals. This chapter discusses the evolution of energy efficiency regulations in the EU, focusing on SRI derived from EPBD and EED.