The Ontario Power Authority is responsible for ensuring a reliable, cost-effective and sustainable supply of electricity for Ontario.  Its main activities are focused on strategic co-ordination of conservation efforts across the province, planning the power system for the long term and ensuring the development of needed generation resources.

The OPA is an integral part of the Ontario electricity system and there are a number of other companies, agencies and regulators with clearly defined roles.

• Regulation:  The Ministry of Energy has over-all responsibility for setting policy direction and for regulating the energy market.  The Ontario Energy Board  (OEB) is responsible for regulating the electricity and natural gas sectors
• Operation:  The OPA is responsible for ensuring a reliable and sustainable supply of electricity for Ontario.  The Independent Electricity System Operator  (IESO) manages the day-to-day reliability of operations
• Generation, transmission and distribution:  Ontario Power Generation (OPG) and private companies produce electricity using a variety of fuel sources.  Transmitters, particularly Hydro One, move power across long distances to where it is needed and more than 80 distributors (including Hydro One) delivery electricity to homes and businesses
• Retailers:  There are a number of retailers who delivery electricity to consumers, including First Nations and Metis communities.

The modern era in Ontario’s electricity began in 1906 with the formation of the publicly owned Ontario Hydro Electric Commission by Sir Adam Beck

This new commission subsequently built what was then the world’s largest hydro-electric dam at Niagara Falls. The energy from this facility provided at-cost power for business and residential use and helped to lay the foundation for Ontario’s prosperity for the next few decades.

Accessible waterpower sites were largely exported by the 1950s. To address this, the HEC began constructing coal-fired generation stations. Later it launched plans to build nuclear power plants. The HEC was renamed Ontario Hydro in 1974.

In 1979, the Porter Commission suggested that demand management, not supply planning, should be the focus in Ontario electricity planning.  A report was subsequently issued by Ontario Hydro but its projection for a significant supply gap was undermined by the economic recession of the 1990s and the coming into service of the Darlington nuclear plant.  As a result, the plan was withdrawn and no additional generating capacity was added. In 1995, the Macdonald commission recommended that Ontario Hydro’s monopoly in generation be eliminated and the electricity market be opened to competition.  

Ontario Hydro was broken up in 1998 with OPG assuming its generation responsibilities and Hydro One its transmission and distribution duties.  The IESO assumed responsibility for system reliability. The OEB continues to regulate the electricity sector.

The market system opened in May, 2002. For a variety of reasons, prices rose and the government imposed a four-year price cap.

In 2003, the government appointed a task force to address concerns about the adequacy of supply after a decade in which no generation capacity had been added despite increased demand.

In 2004, the Legislative Assembly passed legislation that provided for the creation of the Ontario Power Authority to procure new generation, initiate conservation measures and craft a long-term plan for the electricity sector.