Spain's grid operator denied on Wednesday dependence on solar power was to blame for the country's worst blackout, while Prime Minister Pedro Sanchez came under increasing pressure to explain what went wrong.

Electricity is pulsing through Spain and Portugal again after a massive outage knocked out power in both countries on Monday. So too are questions.

Spain is grappling with its most severe blackout, sparking a debate over the role of renewable energy and grid stability. As Prime Minister Pedro Sanchez promises an investigation into the outage, both political and energy sector leaders dispute the causes,