This paper deals with the effects of equipment reliability consideration to thermoeconomic analysis of a combined power and multi stage flash water desalination plant. Exergy and thermoeconomic models of the considered process units are developed and presented in this work. An economic model of the system is developed according to the Total Revenue Requirement (TRR) method. This application can be very useful, either for the plant management in order to achieve a cost-effective operation, or for a better plant design. Equipment reliability using the state-space and the continuous Markov method is incorporated in thermoeconomic analysis to improve the cost values. The results show that the power and water costs with reliability consideration increased 4.1% and 6.4%, respectively. Additionally, the sensitivity analysis shows the relationship between the production cost and the system availability which can help the designer to decide how to improve the profit or competitiveness. (C) 2011 Elsevier B.V. All rights reserved.