Nonetheless, the special characteristics of this segment (strong growth, rapid technical progress, and highly changeable regulatory frameworks) mean that the business model still differs from the rest of the sector, and it is largely controlled by specialized firms. Many of the large electricity firms that invest in this segment do so through specialist subsidiaries, such as Enel Green Power, CPFL Renovaveis or Iberdrola Renovables, which recently has been reabsorbed by the parent company for financial reasons. These barriers are lowered still further if the project is mainly financed with debt, as is usually the case, thereby reducing the capital contribution necessary from the firm in question to no more than 30% of the total cost. This level of leverage is possible because most wind farms have been developed with long-term PPAs, and because nearly all of the production cost is fixed capital which is invested at the start of the project. In terms of wind power, the turbines account for 70% of the cost (BNDES).