This article introduces the energetic macroscopic representation (EMR) as approach for the dynamic nonlinear modeling of a reciprocating air compressor. EMR has been introduced recently for research development in complex electromechanical systems and is based on action reaction principle. The compressor is divided into simple subsystems including: driver mechanism, cylinder head, valves and reservoir. Models are developed for different subsystems, which are assembled into a final overall system EMR. Since the final application of this model will be an isothermal Compressed Air Energy Storage system (CAES), special attention has been paid to transient heat transfer considering the thermal resistor and capacitor effect of the walls adopting a thermoelectric analogy. The results were verified both using Finite Element method and experiment. The EMR modeling presented here allows the modeling of multi-physics components and highlights the interactions of the electromechanical, heat transfer and fluid mechanics phenomena that occur simultaneously in an air compressor.