Why did the lights go out in Spain and Portugal?

“As the two networks have gone down they will have to be re-powered, which means that the grid operator will slowly bring on key generators matched with users (so that production and consumption of electricity match) in regions of the network that slowly expand, until the whole system is back on and can then be reconnected to external networks.”

Why are the power systems linked?

Spain and Portugal have tightly linked power systems with few cross-border links to France and the rest of the EU.

The European Commission, the EU’s executive, has long wanted to change that fact, strongly encouraging EU countries to build more interconnections. Officials argue the move would improve energy security and ease electricity flows across borders. Madrid, Lisbon and Paris have repeatedly signaled a willingness to move forward with that plan, but advances have been slow.

Although Spain and France are now finally forging ahead with a new link in the Basque country, the EU’s energy regulator association warned last year that not enough electricity transmission capacity has been freed up, despite legal requirements to do so. 

It remains unclear whether more connections to Europe would have ameliorated the blackout. 

On one hand, more cross-border links could have strengthened Spain’s ability to balance supply and demand and import electricity, said Pratheeksha Ramdas, a senior power analyst at the Rystad consultancy. Madrid’s current limited trading capacity with France “constrains rapid response capabilities during large-scale disturbances,” she said.