Overview

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 37,205 MW (transmission-connected)
Source: Reliability Outlook released March 2025
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 (2021) 5.3 million
Transmission Lines 30,000 km
Ontario Import Capability More than 6,000 MW
Ontario's Electricity Market $23 billion in financial transactions per year
Average Weighted Wholesale Market Price (2022) 4.78¢/kWh
Global Adjustment Class B Rate (2022) 5.20¢/kWh
Total Annual Energy Consumed (2022) 137.57 TWh
1 Gigawatt hour (GWh) = 1 million kWh
1 Terawatt hour (TWh) = 1,000 GWh

Energy Output

Pie chart - Energy Output by Fuel Type - Year 2024

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