Full-scale wind turbine technology has been widely developing in the recent years and condition monitoring techniques assist at the scope of making 100% technical availability a realistic perspective. In this context, several retrofitting techniques are being used for further improving the efficiency of wind kinetic energy conversion. This kind of interventions is costly and, furthermore, the estimation of the energy enhancement is commonly provided under the hypothesis of ideal conditions, as for example absence of wakes between nearby turbines. A precise quantification of the energy gained by retrofitting is therefore precious in real conditions, that can be very different from ideal ones. In this work, three kinds of retrofitting are studied through the operational data of test case wind farms: improved start-up through pitch angle adjustment near the cut-in, aerodynamic blade retrofitting by means of vortex generators and passive flow control devices, extension of the power curve by raising cut-out and high wind speed cut-in. SCADA data are employed and reliable methods are formulated for estimating the energy improvement from each of the above retrofitting. Further, an insight is provided about wind turbine functioning under very stressing regimes, as for example high wind speeds.retrofitting; further, for some reason as in one of the test cases of the present work, it might happen that the approach can't be employed at all. One might therefore possibly invoke other kinds of precision modeling of wind turbines power curve. It actually is a very fertile field in the scientific literature [14][15][16][17]: as regards these models, the main drawback for their application to the study of wind turbine upgrades is that they are too complex and not enough flexible to be applied to the range of different criticality that the study of wind turbine upgrades poses.The above shortcomings are both circumvented in the present study: this work actually is a collaboration between academia and industry. The industry is Renvico srl 1 , owning and managing 335 MW of full-scale wind turbines in Italy and France. Some wind turbines owned by Renvico have been retrofitted in several ways: this has been a pilot test and the decision of extending the retrofitting to the other wind turbines in the corresponding wind farms has been based on the assessment, coming from this study, of the real profit on the pilot test cases. The SCADA data from the retrofitted and non-retrofitted wind turbines from the wind farms of interest have therefore been shared with the University of Perugia. This academia-industry collaboration, as shall be shown in the next Sections, has produced methods for the study of power curve upgrades, standing at the frontier of the scientific debate and being as well integrable in the everyday industrial management of the wind turbines. This kind of studies on this subject, basing on operational data, has been very recently developing in the scientific literature: in [18], a kernel plus method is adopted for computing ...