Power generation using a simple-cycle gas turbine as the prime mover usually suffers from low efficiency. Associated with low efficiency is a high exergy loss through flue gases. To recover this kind of useful energy (or exergy) from the exhaust gases of a simple-cycle gas turbine generation unit, three different cogeneration systems are presented and evaluated. A computer program was developed to perform the thermodynamic and thermoeconomic analyses. The results indicate that the retrofitted system implemented with steam-injection and regeneration technologies was the best out of tested systems in terms of thermodynamic performance. In this study, the performance exceeded the criteria to become a qualified CHP system. The cost of electricity calculated from the same system is also the lowest under the local energy cost structure and practical operation patterns.