Under the deal, Iberdrola pledges to purchase 50% of its wind turbines from Gamesa Eolica between 2013 and 2022, or up to a total of 3,800MW.
Iberdrola said the new deal also contemplates future collaboration in offshore wind power, and the companies will also jointly develop new maintenance services to improve efficiency.
Iberdrola already has about 9,000MW of capacity from the nearly 13,500MW it has installed worldwide using Gamesa wind turbines.
