Wind propulsion technology has the potential to significantly lower the fuel consumption of cargo vessels and improve the EEDI/EEXI. The number of wind propulsion installations is predicted to increase rapidly the coming years, and thereby the number of different technologies and makers. This development calls for standardised procedures for validation of the wind propulsor performance in fullscale. However, such standard procedures or guidelines are still lacking. This paper proposes a methodology based on short sea trials, combined with digital twin modelling and statistical voyage analysis. The method is demonstrated using full scale trials for three cargo vessels with wind assistance technology. Various strategies for conducting as well as analysing the trials are discussed.