Overview of Sector Roles

Ontarians use more than 140 million megawatt hours of electricity a year to run their homes, businesses, hospitals, schools, transit and infrastructure. Ensuring there is enough energy to meet Ontario’s needs 24 hours a day, 7 days a week, requires the close co-ordination of the many moving and integrated parts of the electricity system. This page describes the different entities and the roles they play to ensure the system is always ready to meet Ontario's electricity needs now and into the future.

System and market operator

The Independent Electricity System Operator (IESO) works at the heart of Ontario's power system as the system operator—directing the flow of electricity across the grid and administering the wholesale electricity market. It sets the hourly Ontario electricity price and ensures there is enough power to meet the province's energy needs in real time. The IESO works with stakeholders and communities across the province to plan and secure energy for the future, as well as guide the conservation efforts in Ontario.

The IESO manages Ontario's electricity market and system in real-time.

Read more about the IESO’s roles and responsibilities in the Ontario electricity system.

Learn more about how the market works and the electricity price is set.

Sending electricity to consumers


The Ontario electricity grid is made up of transmission lines criss-crossing the province delivering electricity from generators to cities and communities. Transmission lines equal to or greater than 50 kilovolts are part of a network called the high-voltage transmission system. The IESO directs the flow of electricity over these lines, while transmission companies own, operate and maintain the lines and towers.

Large industrial consumers that are connected to the high-voltage grid purchase wholesale electricity from the Ontario electricity market.

Local distribution companies (LDC) own and operate additional infrastructure to convert high-voltage electricity to lower voltage, through the use of transformers, and deliver electricity through distribution lines for residential and small business customers. These customers can also choose to purchase electricity from retail sellers, as opposed to their local distribution company, but the physical electricity is still delivered by the LDC.

Learn more about Electricity Pricing including retailer contracts.

Find Your Local Distribution Company

Energy supply

Collage of generation resources

There is currently more than 38,000 megawatts (MW) of electricity built  in the province, supplied by large generators connected to the high-voltage transmission grid. Approximately 3,400 MW come from smaller scale generators and connected to the distribution grid. These small facilities may be on homes, small businesses and farms. About forty percent of Ontario’s electricity capacity comes from renewable resources such as wind, solar, water and biofuel. With the shutdown of the last of the province’s coal generators in 2014, the balance of electricity is generated by lower emission fuel sources such as nuclear, and natural gas and renewables.

The IESO has a role in planning for and competitively procuring resources that meet Ontario’s needs today and into the future. These may be met through diverse resources such as wind, solar, hydro, biomass, nuclear, natural gas, demand response, conservation or other innovative technologies.

Read more about Ontario's supply mix.


An Ontario-Quebec interconnection.

Ontario’s high-voltage lines are connected with neighbouring provinces and states to allow electricity to be imported into and exported out of the province. These interconnected lines (or interties) are connected with Manitoba, Quebec, New York, Michigan and Minnesota. Being part of a large, interconnected system improves reliability as each jurisdiction can rely on the others when required to balance supply and demand for the electricity on the grid.

Learn more about imports and exports.

Regulatory oversight

The Ontario Ministry of Energy, Northern Development and Mines establishes energy policy for the province, working to ensure that Ontario’s electricity system functions at the highest level of reliability and productivity. The Ontario Energy Board regulates rates for the delivery of electricity through transmission and distribution wires, as well as the contracted rates for some generation facilities.

Visit the Ministry of Energy, Northern Development and Mines website and the Ontario Energy Board website to learn more.