Power quality mitigation devices play an important role in lots of industrial segments. Although there were many devices available in the market, the selection of an appropriate device specially for voltage sags and interruptions mitigation has been a challenge in the utility and customer for several years. It usually depends on technical and economic characteristics of the device. Nevertheless, most mitigation method is selected by rule of thumb or empirical method. In this paper, the expected sag frequency for a sensitive load was predicted by stochastic analysis then the life cycle cost analysis for the probabilistic risk assesment of voltage sag mitigation method is performed. Although the economic evaluation of power quality mitigation devices can never be specific, the optimal selection of devices used to mitigate power quality disruptions can be more effectively analyzed by probabilistic risk assessment.