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Market Information


IESO Information

The Independent Electricity Supply Operator (IESO) is an independent, non-profit organization that is responsible for the day-to-day operations of Ontario’s electricity system. The IESO ensures there is adequate electricity for consumers at all times, including importing as required.

During periods of peak demand when supplies of reserve power are low, the IESO may issue public appeals for consumers to reduce consumption. Any reduction in transmission or generation availability or any increase in demand could create shortfalls of electricity and require action such as voltage reduction on the province-wide system. Reduce consumption requests are usually issued during the summer months, when air conditioners are turned up to combat heat and humidity.

For more information regarding the IESO and its functions, visit, or contact them at 1-888-448-7777.

Electricity Facts

Ontario’s System-Wide Electricity Supply Mix: 2015 Data

Electricity sources Ontario’s Electricity Mix *
Water power 23.2 %
Alternative power sources 8.7 %
– solar 1.9 %
– wind 6.4%
– biomass 0.4%
– waste 0%
Nuclear Energy 57.8 %
Natural Gas ** 9.7 %
Other 0.5 %

* Includes both Tx (direct) and Dx (embedded) connected generation (Ontario Ministry of Energy)
** Includes generation from facilities that are predominantly natural gas (e.g., Lennox Generating Station)
Note: Figures may not add to 100% due to rounding.