SOFC is an ideal device for developing distributed combined heat and power (CHP) systems. In this paper, kW-class SOFC system models based on semi-empirical SOFC stack model were established to optimize the systems with the aim of maximizing the system electrical efficiency. Four types of SOFC-CHP systems using different fuel including natural gas (NG), hydrogen, methanol, syngas were compared, and the relationships between key parameters and system energy effciency were analyzed. Simlulation results show that decreasing the air inlet temperature (AIT) and increasing stack temperature will promote electrical effciency most significantly. In addition, the operational costs of four different systems were also compared, and among which the methanol-fueled system was the lowest.