In this study, the performances of a simple and an air preheated cogeneration cycles in ambient conditions are compared with each other. A computer program written by the author in FORTRAN codes is used for the calculation of the enthalpy and entropy values of the streams, Exergy analysis is done and compared for the simple and the air preheated cogeneration cycles for different ambient conditions. The two cogeneration cycles are evaluated in terms of heat powers and electric, electrical to heat ratio, heat exergy, and exergetic efficiency with respect to humidity, temperature, and atmospheric pressure. The simple cycle is better in obtaining high heat rate and heat exergy than the air preheated cycle. The effects of all ambient conditions on these cycles are considered and compared with each other in this study.