Abstract: A method and system are provided for monitoring performance parameters of a hydroelectric power generation facility and determining economic impact of operating the facility at levels other than predetermined reference levels. Optimal or desired levels of parameters of interest are stored in a memory circuit coupled to a central processing circuit. Actual values for the parameters of interest are sensed and communicated to the central processing circuit. Various monitoring circuit modules may be created for specific parameters of interest. The monitoring circuit modules compare the reference values to corresponding actual values and determine deviations from the desired parameter levels. A costing circuit applies an economic impact factor to the deviation values to determine the economic impact of the deviation. The technique may be used to evaluate past or present performance, predict future performance, schedule maintenance, predict payback for plant improvements and the like.