Nowadays more and more researches are aimed to develop equipment, systems and processes energetically efficient generating less environmental impact. In this scenario, this paper proposes the study of five different types architectures for trigeneration systems, using heat reject from an internal combustion engine powered by natural gas. Those architectures are applied to the demands of electricity, refrigeration and heating of the following facilities: Hospital de Clínicas da Unicamp, a major hospital in Brazil; a commercial complex in Hong Kong and a five stars hotel in Tianjin, China. In order to have a better understanding, the energy balance calculations are based on EUF energy utilization factor, one of the parameters availables in the literature to evaluate the performance of that kind of system. In the end, was verified the efficacy of those architectures on the reduction of the amount of primary fuel consumed by the facilities in comparison to systems without trigeneration, (average reduction of 36 percent, at best), when disconnect of the external electrical supply.