The IESO manages the province's power system so that Ontarians receive power when and where they need it. It plans and prepares for future electricity needs. A not-for-profit entity established by the Government of Ontario, IESO fees and licences to operate are set by the Ontario Energy Board.

Electricity Data Fast Facts

Installed Capacity 38,644 MW (transmission-connected)
Source: Reliability Outlook released December 2020
Record Summer Peak 27,005 MW (August 1, 2006)
Record Winter Peak 24,979 MW (December 20, 2004)

Ontario's peak energy use is typically in the summer months when people use air conditioners to beat the heat. Peaks also take place in the winter when the weather is especially cold. Weather has the biggest influence on electricity demand.
Consumers Served 4.9 million 
Transmission Lines 30,000 km
Ontario Import Capability 4,500-5,200 MW
IESO Wholesale Market $18 billion in financial transactions per year
Average Weighted Wholesale Market Price (2019) 1.83¢/kWh
Global Adjustment Class B Rate (2019) 10.8¢/kWh
Total Annual Energy Consumed (201) 135.1 TWh
Energy Efficiency Results 2019 In 2019, Ontarians achieved 0.93 TWh of energy savings through Save on Energy programs.
1 Gigawatt hour (GWh) = 1 million kWh
1 Terawatt hour (TWh) = 1,000 GWh

Energy Output by Fuel Type 2019

Output by Fuel Type: Nuclear 61%, Hydro 25%, Gas/Oil 6%, Wind 7%, Biofuel <1%, Solar <1%

Note: Most solar facilities are connected to distribution systems, not the transmission system. Due to rounding, percentages may not add to 100.