Over 1.5 million Americans were without power today as storms and sub-zero weather gripped the country. The ageing electrical grid is expected to come under further pressure by nightfall, leading to questions about how companies like National Grid, PG&E and ConEdison are policed, and fined, when foreseeable events lead to major outages.
The energy companies will be lining up their excuses, but as a vital part of national infrastructure, their obligation is to predict and prepare for weather events.
Check out our short video history of the US Grid for the full background