A massive power outage appears to have affected large portions of Spain and Portugal Monday. Red Electrica, the operator of Spain's power grid, said on social media Monday morning that voltage has been recovered in substations in several areas in the north,

For millions of people across Spain and Portugal, power was lost in an instant yesterday. Communications came to a halt, water was not running in places, metro systems ground to a standstill, and travellers were strained in airport departure lounges.

Victor Becerra, professor of power systems engineering, at the UK's University of Portsmouth, said the Iberian outage showed the complexity of managing modern energy systems particularly as they integrate increasing levels of intermittent renewable energy, such as wind and solar.