The Independent Electricity System Operator (IESO) balances the supply of and demand for electricity in Ontario and then directs its flow across the province's transmission lines.
The IESO works at the heart of Ontario's power system, connecting all participants − generators that produce electricity, transmitters that send it across the province, retailers that buy and sell it, industries and businesses that use it in large quantities, and local distribution companies that deliver it to people's homes.
Power to Ontario. On Demand.
Ontarians use more than 140 million megawatt hours of electricity a year.
Over the last decade, the IESO has been immersed in the evolution taking place in Ontario’s electricity sector. Serving as the hub connecting generators, traders, transmitters, distributors
and large consumers, the IESO has encouraged and embraced change
− focusing its efforts on supporting a more sustainable and diverse power system.
Ontario’s IESO works to ensure that sufficient electricity is available whenever and wherever it’s needed. Ensuring there is enough energy to meet that demand is an ongoing and highly complex process, requiring the close coordination of all parts of the system.
Every five minutes, the IESO forecasts electricity demand throughout the province and directs generators to provide the required amount of electricity to meet that demand. It can also reduce demand by calling on large volume users to cut back on consumption. This process of balancing supply and demand repeats itself 24 hours a day, seven days a week.
Operating from its Control Centre, the IESO maintains reliability in real time and into the future, while supporting Ontario's green energy policies for the integration of renewable sources of energy.
At all times, the IESO works closely with and coordinates activities with system operators in other jurisdictions to ensure energy adequacy and security across North America.
Looking ahead in cycles of 18 months, the IESO provides forecasts and evaluations of Ontario's current and short-term electricity needs, as well as the adequacy and reliability of the integrated power system to meet those needs.
An audit by the North American Electric Reliability Corporation cited the IESO as a model for system operators, while a peer review showed that its practices in enforcing reliability are exemplary.
Operating and Settling the Wholesale Electricity Market
Every five minutes, the IESO forecasts the level of demand throughout the province. Based on the bids and offers from consumers and generators, the IESO determines the price of energy and the amount to be consumed or supplied by each participant. The IESO also administers the set of Market Rules that governs the operation of the wholesale electricity market.
The IESO settles $12 billion in electricity charges annually.
The wholesale electricity market encourages large consumers of electricity to shift consumption away from periods of high demand.
The IESO allows impartial access to the wholesale electricity market and IESO-controlled grid. It ensures that information is accessible, transparent and relevant and that its services provide the support needed for effective participation in the market. The IESO strives to work with all parties in the sector, to be impartial and transparent. It recognizes the need for an increasing role for consumers in Ontario’s electricity marketplace.
In its role as the Smart Metering Entity, the IESO is responsible for the central data repository (known as the MDM/R) that manages the consumption data for residential smart meters. For more information, please visit
The IESO oversees the emergency preparedness and power restoration activities for Ontario’s power system, including coordinating the restoration and preparedness plans of its market participants.
Ontario Electricity Emergency Plan sets out the overall framework for the electricity industry's emergency planning and response. It is developed and reviewed in collaboration with industry stakeholders.
Evolving the Market
Ontario's energy and environmental needs are changing. The IESO supports the development of new approaches to managing Ontario's electricity system. Engaging stakeholders is an integral part of the IESO decision-making process – individuals and organizations have an opportunity to provide input and feedback about changes that affect their business and help to evolve the market for the benefit of all.
Further enhancements will strengthen the overall market, enhance reliability and provide Ontarians with greater access to information about their power system.
Working in Consultation on a Vision for the Sector
The IESO, its industry partners and stakeholders are working together on a new, shared vision for Ontario's electricity sector – a vision that encompasses cleaner supply, smarter delivery systems and more engaged consumers. Significant progress is being made on these fronts and the IESO actively supports plans within the sector to increase the contributions from renewable resources, accelerate smart grid developments and find new opportunities to increase demand-side involvement in the marketplace.
The IESO is a not-for-profit corporate entity established in 1998 by the Electricity Act of Ontario. It is governed by an independent Board whose Chair and Directors are appointed by the Government of Ontario. Its fees and licences to operate are set by the Ontario Energy Board and it operates independently of all other participants in the electricity market.
By-Law sets out its corporate governance and structure.
The IESO Administration Service Charge is currently set at $0.822/MWh.