To popularize the use of desiccant air conditioners in residences, a system that can supply cooled and dried air in summer as well as heated and humidified air in winter is proposed. An evaporative cooler that affords an increase in cooling capacity and the amount of humidification is used in this system. The results of the enthalpy and exergy analyses, performed using a process simulator, showed that significant exergy losses occurred at the blower, heater, and desiccant rotor. In addition, exergy loss occurred at the direct evaporative cooler in heating humidification. Furthermore, it was found that there exists an optimal water temperature that yields peak exergy efficiency from the desiccant rotor.Copyright © 2011 by ASME