Since petroleum's price increases in recent years, the employment of renewable energy has become one of the most important tasks for government's energy policy. To fully use wind power, different wind farms should have appropriate capacity for wind turbine generators (WTG) to get the most wind power and maximum economic benefit. Currently, there are various values for capacity and hub height of commercial WTG. This paper uses three different economical methods to analyze economical outcomes for different wind farms with different parameters for WTG sets prior to the installation of WTG. According to the comparative analyzed results, the influence of Weibull parameters proposed can quickly choose proper capacity for WTG.