In the wake of Europe's largest blackout in decades, commodities investor Alexander Stahel helps us to understand the physics of power grids, and how Spain's celebrated renewable transition became its Achilles' heel. He introduces the “hellbrise” phenomenon—excessive, rather than too little, renewable generation—as he considers the role of grid inertia in preventing minor disruptions from cascading into failures in mere seconds. Spanish energy policy isn’t the first time that green idealism has brushed over the fundamental requirements of reliable electricity, and it is unlikely to be the last. But it has certainly provided a stark example of the dangers that await such an oversight.