Hydraulic power generator is known to offer one of the cleanest energy supply. However, much emphasis in these plants appears to be directed towards condition monitoring (based on typical weekly and monthly data gathering) and less attention is directed towards continuous performance monitoring. This paper offers an invesigative study of the effect of some performance parameters such as inlet and outlet relative flow angles, nozzle angle, hydraulic turbine efficiency on the overall performance of 108 MW station using four identical vertical shaft Francis turbines. The results of the study indicates that for a given energy supply, determined by the available water head, a one percentage point improvement of the turbine efficiency might lead to increased earnings of about 1.25%.