Step-up in rehabilitation: Not a myth, a science

New turbines, model tested, manufactured and site tested according to state of the art techniques, show consistently an efficiency step-up at least equal to IEC 995 prediction. Although some manufacturers have cast doubts about the capability to reproduce the step-up in rehabilitation, we provide evidence that it has been achieved on well conducted projects. We successively analyze major factors, on the model and on the prototype, that influence the step-up. We finally review some examples to illustrate the desired attitudes that will maximize all the benefits of the rehabilitation.