In this paper, a thermoeconomic analysis method based on the First and the Second Law of Thermodynamics and applied to analyse the replacement of an equipment of a cogeneration system is presented. The cogeneration system consists of a gas turbine linked to a waste boiler. The electrical demand of the campus is approximately 9 MW but the cogen system generates approximately one third of the university requirement as well as 1.764 kg/s of saturated steam (at 0.861 MPa), approximately, from a single fuel source. The energy-economic study showed that the best system, based on pay-back period and based on the maximum savings (in 10 years), was the system that used the gas turbine ''M1T-06'' of Kawasaki Heavy Industries and the system that used the gas turbine ''CCS7'' of Hitachi Zosen, respectively. The exergy-economic study showed that the best system, which has the lowest EMC, was the system that used the gas turbine ''ASE50'' of Allied Signal.