The outage disrupted rail services, phone networks and ATMs across the Iberian Peninsula, turning stations, sports centres and airports into temporary shelters.
Some 35,000 train and underground passengers were rescued by emergency workers in Spain.
By early Tuesday, power had been restored to over 92% of Spain, with officials promising full recovery by the end of the day.
Authorities say the cause is still under investigation, but have ruled out a cyberattack.
