Small-scale distributed generation systems are expected to play a vital role in future energy supplies. Subsequently, power generation using micro-gas turbine (MGT) is getting more and more attention. In particular, externally fired micro-gas turbine (EFMGT) is preferred among small-scale distributed generators, mainly due to high fuel flexibility, high overall efficiency, environmental benefits, and low maintenance requirement. The goal of this work is to evaluate the performance of an EFMGT-based standalone polygeneration system with the help of computational simulation studies. The main focus of this work is to develop a dynamic model for an EFMGT. The dynamic model is accomplished by merging a thermodynamic model with a mechanical model of the rotor and a transfer function based control system model. The developed model is suitable for analyzing system performance particularly from thermodynamic and control point of view. Simple models for other components of the polygeneration systems, electrical and thermal loads, membrane distillation unit, and electrical and thermal storage, are also developed and integrated with the EFMGT model. The modeling of the entire polygeneration system is implemented and simulated in matlab/simulink environment. Available operating data from test runs of both the laboratory setups are used in this work for further analysis and validation of the developed model.