Desiccant evaporative systems are heat driven at moderate temperature and are usually coupled with solar collectors or with waste heat. The performance of desiccant systems is very sensitive to outside conditions and to the efficiency of the system components. In this paper the impact of these factors on the performance of two configurations of desiccant systems is investigated through simulation. First, a model of a desiccant air handling unit is briefly presented and validated experimentally. Then different efficiency combinations are studied and the critical efficiencies are derived. Finally, a comparison of the conventional and the recirculation configurations is made, based on outside conditions. (C) 2009 Elsevier Ltd. All rights reserved.