The efficiency of power quality control belongs to the non-direct interest reducing unknown loss and has such features as uncertainty and difficult estimation and brings great uncertainty for the applicability and evaluation result of economic evaluation method of the control scheme. In this paper

the economic evaluation process of the power quality control

net present value method which is mature in the economic evaluation area

investment recovery method

internal return rate method and whole life cycle cost method which are applied in the investment evaluation are introduced firstly. The valuation index of the four method is given and applicability of the above each method in the economic evaluation of power quality control scheme is analyzed in detail. Considering better performance of internal return rate method and the net present value method

the latter is selected and a kind of evaluation method of improving the net present value which is related to efficiency risk control is proposed for the uncertainty problem of indirect efficiency of power quality control. Finally both the applicability analysis and effectiveness of the proposed method in this paper is verified with UPS and DVR as example for certain semi-conductor element manufacturer.