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Hazard · Technical

Power outage

Stay calm: keep the fridge and freezer closed, turn off devices and leave only one switched on to signal the power's return. Use a battery- or crank-powered FM/DAB+ radio for information and check on neighbours who need help. Critical conditions usually only develop after about 12 hours.

A large-scale power outage hits almost everything at once: lighting, heating control, refrigeration appliances, mobile-phone antennas (whose backup power lasts only minutes to a few hours), ATMs, tills and, after a few hours, often the water supply too, because the pumps fail. Electricity is the central dependency of our infrastructure — when it disappears, cascade effects begin.

Triggers can be storms (Lothar paralysed hundreds of thousands of households in 1999), technical faults, grid overload or a Europe-wide shortage. How vulnerable the closely interconnected European power grid is was shown in 2003 by the Italian blackout — triggered by a line in Switzerland.

The longer an outage lasts, the more important preparation and neighbourly help become. The first few hours are usually uncritical; from about half a day on, the cold chain, heating and communications become a problem.

Risk rating

Risk · Medium (level 3 of 5)

Likelihood: Medium · Impact: Medium → Overall risk: Medium.

Risk matrix: likelihood runs vertically (top = high), impact runs horizontally (right = high). The highlighted cell shows this hazard's rating.
Impact
Low Medium High
Likelihood High
Medium This hazard's rating
Low

Legend: Low (green) · Medium (yellow) · High (red). Overall risk is likelihood multiplied by impact.

A blackout cripples heating, communications, payment systems and the water supply – often over a wide area and for hours to days.

Immediate measures

  • Keep a power bank and a crank radio ready
  • Store cash in small denominations
  • Charge important devices in advance

Warning signs

  • Repeated brief voltage dips or flickering (precursors of grid instability)
  • Large-scale storm/severe-weather warning from MeteoSwiss (most common cause: trees falling onto lines)
  • Official appeals to save or OSTRAL notices ahead of a shortage
  • Failure of street lighting / traffic lights in the neighbourhood, dark neighbouring houses
  • The mobile network slows down / fails (antenna backup power runs out)

Before · During · After

Before

  • Keep emergency supplies and water ready
  • Power banks charged, crank radio within reach
  • Cash in small denominations at home
  • Know how the heating behaves without electricity

During

  • Switch off devices, leave one on (signal when power returns)
  • Keep the fridge and freezer closed
  • Use the radio (FM/DAB+) for information
  • Check on neighbours who need help

After

  • Check the cold chain of food
  • Replenish supplies
  • Take notes: what was missing?

This really happened

  1. 2025 Iberian blackout

    On 28 April 2025 the power grid of the Iberian Peninsula collapsed; more than 50 million people in Spain and Portugal were without electricity for around half a day. The investigation report cited voltage fluctuations and an overvoltage cascade; a cyberattack was ruled out.

    Source

  2. 2021 European grid split

    On 8 January 2021 the continental European interconnected grid split into two parts for around an hour after a switch failure in Croatia; the frequency briefly dropped to 49.74 Hz. Swissgrid, as a coordination centre, was involved in restoring it.

    Source

  3. 2003 Italian blackout

    A line at the Lukmanier in Switzerland, knocked out by tree contact / overload, triggered a cascade on 28 September that cut almost all of Italy (around 55 million people) off the grid for up to 18 hours in some places.

    Source

  4. 1999 Storm Lothar

    Switzerland's most severe winter storm interrupted the electricity supply across large parts of the country on 26 December; repair work on the lines took days.

    Source

Frequently asked questions

How do I prepare for a power outage?

Keep emergency supplies with water ready, charge power banks and keep a crank radio within reach. Store cash in small denominations at home and find out how your heating behaves without electricity.

Why is a power outage so dangerous?

Electricity is the central dependency of our infrastructure: an outage hits lighting, heating, refrigerators, payment systems and water pumps all at once. Mobile-phone antennas have only minutes to a few hours of backup power, after which the mobile network often fails too.

What should I do after a power outage?

Check your food for a broken cold chain and replenish your supplies. Make notes about what was missing – this way you improve your preparedness for next time.

Official sources