This paper presents a thermodynamic analysis for energetic and exergetic efficiency with different combinations. The effect of pressure ratio, turbine inlet temperature and percentage pressure drop on net power output, first law and second law efficiency analyzed theoretically is presented. Combined approach of first law and second law is applied. Computational analysis is done in order to investigate the turbine inlet temperature, overall pressure ratio, pressure drop in combustor and heat recovery system generator, evaporator temperature on the exergy destruction in each component, ratio of electrical to thermal first law efficiency and second law efficiency of the system. It was observed that exergy destruction in combustion chamber and HRSG is considerably affected by the pressure ratio and the turbine inlet temperature, but it is unaffected by evaporator temperature and pressure drop. As the pressure ratio increases, the first law efficiency of cogeneration and trigeneration, decreases but the second law efficiency and the electrical to thermal energy ratio for these systems increases with the same. The first law efficiency, electrical to thermal energy ratio and the second law efficiency of cogeneration and trigeneration increase with the increase in turbine inlet temperature. Also the exergy destruction in combustion chamber and heat recovery steam generator decreases significantly with the increase in pressure ratio but increases with the increase in turbine inlet temperature. It was observed that a trigeneration system gives 20 − 40% higher efficiency than cogeneration. Such systems are useful in restaurants, hospitals, process industries, chemical plants, dairy industries etc. having constant demand of electricity, heating and cooling throughout the year.