Managing the Power System

The IESO is the coordinator and integrator of Ontario’s electricity system. Our system operators monitor the energy needs of the province in real time – 24 hours a day, 7 days a week – balancing supply and demand and directing the flow of electricity across Ontario’s transmission lines.

A Reliable System

The IESO works with our partners in the electricity sector, as well as our Canadian and U.S. neighbours, to ensure that Ontario’s grid operates reliably and that everyone in Ontario has access to the energy they need, when and where they need it.

Ensuring Reliability

The IESO is responsible for ensuring these five pillars of electricity system reliability are met:

  • Capacity: The ability to produce enough electricity to meet demand
  • Energy: The ability to produce electricity consistently over time
  • Transmission: The ability to distribute and deliver electricity
  • Operability: The ability to respond to changes in demand
  • Ancillary ServicesTechnical support that fine-tunes the electricity grid to adapt to second-by-second changes in demand.

A Province-Wide System

Hundreds of electricity resources across Ontario are connected directly to the provincial electricity system. During the day, the IESO sends dispatch instructions across the system: in response, electricity suppliers adjust their output up and down as needed.

Because the IESO controls all dispatch instructions for the province, our system operators can ensure that Ontario’s electricity suppliers are not over or under producing at any given time and that the system is running as efficiently and cost-effectively as possible.

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Balancing Supply and Demand

It is important to closely match how much energy we have (supply) with how much energy we need (demand). Deciding what electricity resources to use, and when, depends on many factors:

  • Current electricity demand
  • The location of generators in relation to where electricity is needed
  • The maximum amount of energy our transmission lines can carry
  • Power plant maintenance schedules
  • The cost to produce electricity

A Redundant System

Power plants and transmission lines, just like all mechanical equipment, require maintenance. Electricity generators share their maintenance schedules with the IESO to review and ensure that they will not interfere with the system’s ability to provide Ontario's energy needs. The IESO also evaluates what kind of impact unplanned outages would have and if the system has the ability to handle emergency situations.

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Prepared for Emergencies

The IESO oversees the emergency preparedness and power restoration plans for Ontario's power system. In collaboration with our electricity sector partners, the IESO maintains the Electricity Emergency Plan, which sets out Ontario’s emergency response approach.

Overseeing the Market | About the IESO

The IESO administers, settles and evolves Ontario’s wholesale electricity market to foster competition and ensure affordable electricity pricing.