The deregulation of the energy market has created an additional incentive for gas turbine plants operators to minimize and control performance deterioration with respect to the economical aspects of the plant. The most prevalent deterioration problem is compressor fouling, which has a significant impact on the power plant profit. Off-line washing is able to recover the engine's performance losses due to fouling, but has a variety of associated costs. A method to predict the impact of the compressor washing process on the power plant revenue is presented herein, allowing for the optimization of the process with regards to power plant specific data. For this reason, a detailed cost analysis module is formed and coupled with an engine model allowing for the study of both economic parameters and engine operation parameters like the increase of maintenance cost due to start-ups and the variation of the engine degradation rate. The method is applied for the case of an aeroderivative gas turbine of 42 MW. The parameters associated with the off-line washing process and the engine performance that affects the plant's revenue are examined and discussed, while recommendations on the optimal washing schedule are made. (C) 2012 Elsevier Ltd. All rights reserved.