Organic Rankine cycle (ORC) is a promising technology for converting low-grade waste heat into the electricity. This paper carries out an exergoeconomic analysis and performance optimization of a condenser for a binary mixture of vapors in the ORC system. In this model, the exergy loss due to heat transfer between a binary mixture of vapors and the cold fluid is taken into account and other exergy losses such as pressure drop and flow imbalance are ignored. The objective function is defined as the annual total cost per unit heat transfer rate considering the capital cost and the exergy loss cost. The variation laws of the annual total cost with the number of the transfer unit and the temperature ratios are exhibited. The optimal values of the number of the transfer unit and the heat capacity ratio which minimize the annual total cost have been obtained. The effects of related technical and economical parameters on the optimal performances have also been discussed. (C) 2012 Elsevier Ltd. All rights reserved.