During the recent years, the use of new materials and enhanced production processes led to successively increasing sizing parameter namely rotor diameter, rated power and hub height of wind turbines as well as decreasing initial and running costs. The thereby risen market share shows that wind energy projects are an interesting field for financial investors. In this connection the question arises, how investors benefit from the mentioned technical developments. Regarding the utility maximization of investors in turbine projects, goal of this survey is to determine the economically optimal turbine configuration in contrast to the technically feasible by maximizing the net present value. For this purpose, a generalized approximation of the power curve of three-bladed, direct-driven, variable speed horizontal axis wind turbines is applied. For estimation of the economic parameters, a complex mass cost-model is used for determination of the initial costs as a function of the sizing parameter. Thereby, a method is shown for adjustment of this model to several differences in price levels of the different turbine components. Furthermore, detailed relationships for running costs as well as the estimation of the cost of equity capital are shown. Due to the current importance of feed-in tariff, revenues for electricity sale depend on the German "Renewable Energy Act". The calculation of economically optimal sizing parameter first is done for a reference site in conjunction with a sensitivity analysis to determine the most influential sizing parameter with respect to economic viability. Afterwards, a range of typically onshore wind speeds in Germany is considered. (C) 2016 Elsevier Ltd. All rights reserved.