Ontario’s measured load drop and recovery during the 2003 blackout

Ontario’s demand measurements cover a seven-minute interval

The IESO chart records 24,099 MW at 16:10 and 2,574 MW at 16:17, a difference of 21,525 MW. That is the change between two Ontario observations. It helps describe the abrupt loss of service in the province. Source 1

The interrupted-load estimate covers the wider outage

The IESO reports roughly 61,800 MW of customer load interrupted across the affected area, which included Ontario and parts of the northeastern United States. Its population estimate is more than 50 million people. The Ontario chart covers one portion of that larger event. Source 1 Source 2

Restoring the system and normal generation took different amounts of time

IESO reports Ontario’s power system was restored within 30 hours. The province remained under a state of emergency until 22 August as generation returned to normal capability. IESO says homes and businesses reduced peak demand by 15% to 20% each day during the public appeal. Source 1

The outage also led to a joint review

The governments established the task force on 15 August 2003. It published its final report in April 2004. That publication is a post-event milestone, distinct from the dates when Ontario residents regained service or the system operator ended its conservation appeal. Source 3 Source 1

Sources

• Ontario Independent Electricity System Operator 2003 blackout and restoration record
• US Department of Energy August 2003 blackout record
• Government of Canada announcement of the joint task force final report