At the start of the 20th century, the country faced a serious problem in that domestic coal was expensive, and of low quality.  With high tariff walls, that meant that electricity was costly.  So as the start of the 20th century, there was massive investment in hydroelectric.  This basically covered demand until the 1960s, when the economic miracle took hold.

At that time, Spain turned to petroleum fired plants to cover new demand. At the time petroleum was a cheap alternative to coal. Understandably, they got shellacked come the oil crisis. There had been a a number of nuclear facilities planned at the start of the 1980s, but there was local opposition.  ETA got the idea that this was an issue that they could latch on to.  And....  they killed some of the workers at the planned Lemoniz plant. The government abandoned the expansion shortly thereafter.  At this time, there was a movement towards combined cycle gas plants during the  80s and 90s.  Again, gas was a cheap alternative.  That began to come to an end.  Finally, Spain moved to develop windpower in the late 1990s. The drive to build up renewables has a lot to do with the relative energy poverty of the Iberian Peninsula.  

And I'll give my consent to any government that does not deny a man a living wage-Billy Bragg