The Global Centre for Risk and Innovation (GCRI)
Large outages come from storms, wildfires, heat, ice, floods, earthquakes, geomagnetic storms, equipment failure, operator error and cyberattack. How long they last depends less on the cause than on how quickly the grid can be restarted and repaired. This page sets out how outages unfold, how black start and restoration work, how critical services are prioritised, and what evidence operators, regulators and civil protection authorities use.
GCRI · Established · service level R0
Blackouts are losses of electricity supply over a wide area, caused by storms, wildfires, heat, ice, floods, earthquakes, geomagnetic storms, equipment failure, error or cyberattack. How long they last depends on how fast the grid can be restarted and repaired. Restoration follows black start plans and priorities for critical services.
Where demand concentrates in cities and the rail, road and port corridors that move fuel and equipment, shown for Ukraine as an example geography for this subject.
The working screen behind this subject: its structure, terms and states. Names are placeholders and values illustrative.
Outages, black-start and critical service restoration. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
Wind, ice and falling trees bring down distribution lines; floods inundate substations; wildfire risk forces preventive de-energisation. Distribution damage usually causes most customer outage minutes, while transmission failures cause the widest outages.
After a system-wide collapse, operators restart from units that can start without external power, such as hydropower, some gas turbines or batteries, then energise transmission paths and pick up load in steps while holding frequency stable.
Hospitals, water works, telecommunications and fuel stations depend on backup generators with limited fuel. Mobile networks fail as site batteries run down, which slows the very restoration that depends on communications.
Restoration is limited by crews, spare transformers, road access, fuel logistics and communications. Large power transformers take a long time to manufacture and move, so spares and mutual-aid agreements largely decide recovery time.
Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.
| Term | Definition |
|---|---|
| Restoration curve | The share of customers or load without power plotted over time from the start of an outage to full recovery. |
| Customer minutes lost | The total minutes of interruption summed across all affected customers. |
| Black start capability | Generators contracted to restart without grid supply and energise the network after a shutdown. |
Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.
| Indicator | Unit | Cadence | Source type | Label |
|---|---|---|---|---|
| Customer minutes lost | customer minutes | per event | Utility outage management systems | OFFICIAL |
| Customers without power over time | customers | hourly during events | Utility outage reporting | REPORTED |
| Restoration curve | percent of customers restored against elapsed hours | per event | Utility and regulator event reports | REPORTED |
| Loss of night-time lights in the affected area | change in radiance | daily | Satellite night-time lights | OBSERVED |
| Backup power endurance at critical sites | hours | per asset | Facility and asset registers | OFFICIAL |
| Contracted black start capability | megawatts | annual | Operator restoration plans | DECLARED |
| Mobile network site availability | percent of sites operating | hourly during events | Telecommunications regulator status reports | REPORTED |
The topic as a computational graph: named sources feed the methods, an evidence review gates the outputs, and the decisions stay with the authorities that hold them.
Fig. 02Nodes carry their type, two metric rows and a state; connectors show what feeds what; dashed frames name the owners; the timeline is the cadence. Design of the pipeline, not a record of a run.
Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.
| Source | What it gives | Licence class |
|---|---|---|
| DOE Form OE-417 electric emergency incident and disturbance reports | Major outages and disturbances in the United States | Public domain |
| NASA Black Marble night-time lights (VIIRS) | Daily night-time radiance for mapping outage and recovery | Public domain |
| NERC event analyses and FERC inquiry reports | Reconstructions of major disturbances and recommendations | Public reports |
| ENTSO-E incident classification scale reports and expert panel reports | Classification and investigation of European grid incidents | Public reports, ENTSO-E terms |
| EM-DAT international disaster database (CRED) | Disaster events with their reported infrastructure impacts | Free for non-commercial use, registration |
| FCC Disaster Information Reporting System status reports | Communications outages during activated disasters in the United States | Public domain |
| Utility and regulator outage records | Event timelines, customers affected and restoration progress | Public records or by agreement |
Energy Nexus prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.
| Who decides | The question | Evidence this page serves |
|---|---|---|
| Transmission and distribution operators | How to sequence restoration and which loads to restore first | Restoration plans, dependency maps, backup endurance at critical sites |
| Energy regulators | Whether resilience investment such as undergrounding, hardening or spares is justified | Customer minutes lost by cause, restoration curves, cost and benefit evidence |
| Civil protection and emergency management agencies | Where to send generators, fuel and shelter capacity during a long outage | Outage extent from night-time lights and utility data; critical service maps |
| Hospital, water and telecommunications operators | How much backup power and fuel to hold and how to secure resupply | Endurance records, past outage durations, fuel logistics evidence |
Restoration typically builds islands of supply around black-start plants, then synchronizes them with each other and with neighbouring systems. Each step must keep frequency and voltage within limits while operators work with partial information.
Only some plants can start without grid power. Others need power to run pumps and controls before they can generate.
Crews need telecommunications and fuel, which themselves need power. Backup batteries and generators run down.
Reconnecting load too fast can collapse the partially rebuilt system and restart the process.
Operators maintain restoration plans and test parts of them. Full-system tests are rarely possible.
Network science and resilience engineering map which services need which supply and how long backup lasts. Backup data is often incomplete.
Cross-sector exercises test assumptions between energy, water, telecommunications and emergency services.
Post-event reports remain the main evidence. Their findings are not always comparable across countries.
The current service level is R0: information and enquiries. An enquiry receives a reference and names the next step; applications, payments, compute allocations and registrations open only when their team, terms and review capacity exist.