The origin of Iberduero is in the company Hidroeléctrica Ibérica, which was founded in Bilbao by the engineer Juan Urrutia Zulueta on July 19, 1901, with capital provided by the BBVA.[2] Initially, this company was dedicated to the hydroelectric exploitation of several waterfalls that it built in the north of Spain, mainly in the Ebro basin. In 1944, Hidroeléctrica Ibérica absorbed Saltos del Duero, which had been founded in 1918 to exploit the hydroelectric exploitation of the Douro River in its section bordering Portugal. The merger was completed on September 30, 1944, giving rise to Iberduero S.L.[3]
Iberduero developed a large hydroelectric system, with more than 100 plants, being especially important the one formed by the plants located on the Douro and its tributaries, which included the Aldeadávila, Saucelle, Almendra, Castro, Ricobayo and Villalcampo dams.[5]
The number of subscribers to the company increased from 250,000 at the time of its foundation to 1,400,000 in 1967. The company's largest shareholder since its foundation has been BBVA (Banco Bilbao Vizcaya since 1988).[citation needed]
Merger
In 1990, Iberduero and Hidroeléctrica Española (Hidrola, one of its main competitors) began negotiations aimed at a possible union of their interests, seeking an alliance that would balance the electricity market, which was 40% dominated by Endesa, the same percentage that would be reached by the merger of both companies.[8] The final agreement was reached on May 1, 1991, and the system used was a takeover bid presented by Iberduero for the integration of both companies.[9] At the time of the merger, Hidrola had 418,605,724 shares, and Iberduero had 508,526,934; the agreement stipulated that one Iberduero share would have the same value as one share of the new company, while 5 Hidrola shares would be equivalent to 4 Hidrola shares plus 250 pesetas.[10]