To thoroughly analyze the conditions in power lines, transformers or loads, it is essential to have knowledge of their active and reactive power flow contributions from each power source. Understanding these contributions allows for a detailed analysis of the impact of active and reactive power flow contribution from each power source on active and reactive power losses in each network element, as well as the determination of power participation of each source to every load. This paper provides the necessary equations and an adequate procedure for calculating power flow contributions. The method is suitable for meshed network and considers shunt elements, avoiding problematic simplifications. Furthermore, it ensures impartiality towards any network user, making it well-suited for application in deregulated environments. By offering valuable information useful, this method supports the creation of transparent and non-discriminatory agreements between network operator and users.