With Modeling Solution it is easy to define customized energy systems from a specific equipment to a complex process plant as a significant energy user (SEU) with several variables and energy performance indicators (EnPIs). Of course, energy performance indicators can be defined as functions of variables with access to thermodynamic property tables. There are several function to calculate complex thermodynamic indicators including functions for enthalpies of reaction, constant specific heats for flows with several compositions, steam turbines power and efficiencies, compressors required power and heat exchangers duties. The system can be connected to laboratory and operation databases. Still, data for variables can be provided manually or automatically.