The target of this master thesis is to establish a model of calculating the economic impact of wind speed forecast and real data differences on a projected wind park in the area of Mosonmagyaróvár in Hungary. The Hungarian law prescribes to producers of REN energy a supply forecast, which has to be sent regularly to the grid operator. Based on the forecasted energy delivery and the real delivery a penalty system is applied which leads to certain losses for the owner of the wind park.Based on forecast data from the Hungarian Meteorological Service a model is established which calculates an energy delivery forecast. The real energy production also needs to be simulated but with the wind speed data from the tower. Based on the differences of forecasted and ?real? energy delivery the respective fine is calculated and introduced into the economic model of the wind park. As economic model the structure of a net present value calculation over the projects life-time is applied. The technical and financial data are from an existing project of Energiepark Bruck an der Leitha. The paper will show that the direct usage of the received forecast data is resulting to a high power prediction error and therefore also a high fine to be paid. The impact of this fine to the economics of the wind park is rather significant. It is therefore proposed to further fine tune the received forecast data locally before establishing a power forecast to the grid operator.