Causes
Why the lights go out
A Black Sky event is a loss of power lasting days that takes water, phones, payments and fuel down with it. The UK plans on 72 hours: the grid operator expects to restore power within two to three days of a national failure.
What could cause it
Most to least likelySevere storms and floods
Most likely cause of long local outages. Storm Arwen (2021) cut power to some homes for over a week; Lancaster (2015) lost power for days
Equipment failure
Likely, usually local. Heathrow closed in 2025 after a substation fault flagged in 2018 was never fixed
Cyber attack, now AI-scaled
Rising fast. Several services down at once (banks, NHS, shops) is likelier than one total blackout
Grid cascade
Low. Spain and Portugal went dark in seconds in April 2025 after a voltage-control failure
Sabotage by hostile states
Low, but rising. Russian sabotage of European infrastructure rose in 2026, including undersea cable cuts
EMP or severe solar storm
Very low. A high-altitude EMP needs a nuclear detonation
Why it matters now
- AI removed the cost limit: agents do in hours what took skilled attackers weeks, so far more targets are worth hitting.
- Fallbacks are going: landlines switch off, FM radio is under review, and most mobile masts have little battery backup.
- Households carry the first three days: the Be Ready campaign asks every home to cope alone for 72 hours.
What fails when the power goes
- Water pumps and sewage, so taps can run dry and toilets back up.
- Phones, internet, card machines and cash machines, within hours.
- Petrol stations and traffic lights.
- Heating: a gas boiler still needs electricity.
What it doesn't mean
- There's no public evidence of an imminent attack or a planned blackout.
- Infrastructure going down somewhere for days is likely, and already happens.
- For our family, the likeliest harm is to income, from fraud and from cyber incidents, not a scene from a film.
Infographic · tap to enlarge