The size of the generator of a wind turbine plays a fairly minor role in the pricing of a wind turbine, even though the rated power of the generator tends to be approximately proportional to the swept rotor area. This chapter describes the important economic and physical relations related to economics of wind power. The choice of rotor size and generator size depends on the distribution of the wind speed and the wind energy potential at a prospective location. Capital costs of wind energy projects are dominated by the price of the wind turbine itself. The costs of wind turbine installation include notably: foundations, road construction, underground cabling within the wind farm, low to medium voltage transformers, medium to high voltage substation, transport, craning, assembly and test, administrative, financing and legal costs.