This paper presents a methodology how energy consumption and energy inefficiencies can be quantified for industrial processes based on a general, branch- independent approach for the purpose of increasing energy efficiency. For many companies the information of the actual energy use of their processes is very limited. Therefore, knowledge of energy consumption is only available on an overall basis and the product- specific energy costs are often calculated with a common cost- plus system. This deficiency in information is part of the reasons, why energy efficiency potentials are often neither known nor realized. For that reason a general approach is needed, which (1) uses the actual economic data of a company and (2) combines and compares it with thermodynamic analyses in order to (3) calculate the actual energy consumption of processes and products to (4) identify and quantify the energy efficiency potentials. The suggested general approach is branch- independent and analyses energy efficiency potentials. Firstly this is conducted through a modular- based, three- level industrial model mapping process. Each module contains production units (industrial plant assets), where main industrial processes are integrated into one module. The different modules are then connected on different levels in order to find product- specific production pathways. Secondly, both a top- down and a bottom- up approach are implemented. The top down approach uses economic and overall energy consumption data and transfers it to the modular view. The bottom- up approach applies technical data of the used production units and quantifies energy consumption based on thermodynamic and general technical data. Through this methodology it is possible to derive actual energy consumption of processes and corresponding manufactured products, which furthermore helps to understand energy cost generation for various products. It also divides the possible inefficiencies into a technical and an organisational part which leads to technical, organisational and social measures. The described modelling of industrial processes on a modular, multilevel approach is applied to case studies for several Austrian foundry companies. Actual data is used for (1) building the model (2) evaluate the model and (3) make the actual energy consumption of processes more transparent. The case studies show that important information is concealed through wrong energy allocations and thus prevents the knowledge of energy efficiency potentials. The application of the model approach in foundry companies enables to (1) calculate energy consumption for various important modules, (2) transfer economic and technical data to a process oriented picture of the energy use, (3) calculate energy demand of various products and (4) provides the first basis for energy efficiency potential analysis.