Manufacturing energy flows are characterized by two types of models: an energy process-step model and an energy end-use model. This paper provides a methodology for developing energy process-step models using federal database. Since energy end-use model provides the basis to scale energy process-step model, first, the concept of an energy end-use model is briefly described. Then, a concise methodology to construct the key part of the energy end-use model is given, namely, on-site steam and power generation model. Finally, a thorough methodology to develop energy process-step model showing energy inputs at each step of an industrial process is described by providing reconciliation with the energy end-use model results. An example methodology is provided for nitrogen, oxygen and argon production energy process-step models. Our approach to creating these models has been shown to be applicable to other energy intensive manufacturing industries. When used in conjunction with similar models for other years, these models can be used to identify the changes and trends in energy use.