The overall efficiency of a turbine is the ratio of the:
1
Power developed by the runner of a turbine to the power supplied by the water at the inlet of the turbine
2
Power at the shaft of the turbine to the power developed by the runner
3
Volume of water actually striking the runner to the volume of water supplied to the turbine
4
Power available at the shaft of the turbine to the power supplied by the water at the inlet of the turbine