The current regulatory framework in Europe regarding industrial energy consumption puts emphasis on regular energy assessments and increasing energy efficiency. Among the available strategies to identify energy savings opportunities, Total Site Analysis (TSA) can be a powerful method to generate utility savings in industrial sites or clusters, targeting for heat recovery and cogeneration potential. The grey box representation of the energy requirements focuses on process/utility heat exchanges when defining hot and cold streams. This representation is usually most suitable when carrying out a TSA on large industrial systems, as direct heat recovery schemes are rarely viable. Since its initial problem definition and solving in the 1990s, a high number of theoretical developments and practical applications have expanded the TSA knowledge. Still an important body of work on TSA techniques and case studies only addresses general aspects and issues that are encountered, and no in-depth explanation yet is found on how to consider specific types of heat consumers and producers. This paper presents a methodology for data collection and streams definition in TSA. It provides a step-by- step approach for defining the process and utility requirements of the main types of heat flows typically found in large industrial systems, including their graphical representations. Using the proposed definitions, it is possible to systematically build composite curves for the total site profiles.