Delivering reliable electric service to our customers requires meticulous supply management. We must also make sure that our transmission and distribution systems are reliable and can deliver power efficiently to our various customers in Québec and neighboring markets. For example, we conduct major maintenance and expansion operations. We also control vegetation in our distribution and transmission line rights-of-way and on our dikes and dams.

Electric service quality is measured by the system average interruption duration index (SAIDI), which reflects the average interruption time per customer over the course of a year. Some scheduled interruptions are required for system maintenance; unscheduled outages are caused by bad weather, invasive vegetation or equipment failure.

The system average interruption duration index (SAIDI) measures the average annual service interruption time per customer. The normalized distribution system SAIDI excludes interruptions that are mainly due to extreme weather conditions. The system average interruption duration index is based on an international standard of the Institute of Electrical and Electronics Engineers (IEEE).
Even in extremely cold weather, system reliability and service quality are maintained.


  • Transmission system investments: $2.0 billion. Major investments will continue in the coming years.
  • Distribution system investments: $650 million.
  • Hundreds of line workers, accompanied by mechanics and support staff, were mobilized to lend a hand in New Brunswick, Maine, Georgia and New York State during major outages caused by freezing rain and a hurricane. These missions were conducted under agreements between utilities, including Hydro-Québec, that are members of the North Atlantic Mutual Assistance Group.