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Corporate IESO > Media > Year-End Data > 2011 - Composition of Ontario's Electricity Supply Mix Continues to Change: Consumer Response Supports Reliability


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2011 - Composition of Ontario's Electricity Supply Mix Continues to Change: Consumer Response Supports Reliability

The Independent Electricity System Operator's annual release of supply, demand and price data highlights three trends that helped shape the management of Ontario's power system in 2011: increasing production from renewable resources, reduced dependence on coal-fired units, and a more active role for consumers in managing their consumption. 
With a total installed capacity of more than 1,700 megawatts (MW) at year-end, Ontario's wind generators are playing an increasingly important role in meeting demand for electricity. Total production rang in at 3.9 terawatt hours (TWh) - up substantially from 2.8 TWh in 2010. November 2011 marked the highest monthly wind output ever seen in Ontario, with production in that month alone exceeding 0.56 TWh. In annual terms, wind generation represented 2.6 per cent of total output across all fuel types of 149.9 TWh.

Production from Ontario's nuclear units continues to supply more than half of Ontario's power needs. Nuclear generation rose slightly in 2011 to 85.3 TWh, an increase of 2.4 TWh from 2010. By contrast, output from Ontario's coal-fired units dropped to 4.1 TWh in 2011, two-thirds lower than it was the year before. After unusually low water levels resulted in reduced hydroelectric output in 2010, production rebounded to 33.3 TWh from 30.7 TWh. Natural gas facilities rounded out the mix, with production of 22.0 TWh, up from 20.5 TWh in 2010.

The table below reflects total electricity output in 2011 by fuel type.









85.3 TWh

33.3 TWh

4.1 TWh

22.0 TWh

3.9 TWh

1.2 TWh

56.9 %

22.2 %

2.7 %

14.7 %

2.6 %

0.8 %


82.9 TWh

30.7 TWh

12.6 TWh

20.5 TWh

2.8 TWh

1.3 TWh

55.0 %

20.4 %

8.3 %

13.6 %

1.9 %

0.8 %


82.5 TWh

38.1 TWh

9.8 TWh

15.4 TWh

2.3 TWh

1.2 TWh

55.2 %

25.5 %

6.6 %

10.3 %

1.6 %

0.8 %


84.4 TWh

38.3 TWh

23.2 TWh

11.0 TWh

1.4 TWh

1.0 TWh

53.0 %

24.1 %

14.5 %

6.9 %

0.9 %

0.6 %

Due to rounding, percentages may not add to 100.

Total electricity consumption in Ontario dipped slightly to 141.5 TWh, down from 142 TWh in 2010. A heat wave in late July pushed peak hourly demand to 25,450 MW on July 21 - a 375 MW increase from 2010's peak. This increase would have been even higher if not for demand response (DR) program participants, which include residential, industrial, commercial and institutional users that agree to reduce their consumption during peak periods with extreme weather conditions. During the peak hour, demand for electricity was reduced by more than 500 MW through various DR programs and pricing incentives.

"The supply mix is not the only thing that's changing," said Paul Murphy, President and CEO of the IESO. "By reducing their consumption during periods of high demand, and by using new tools and applications to monitor their usage, Ontario's electricity consumers are becoming key partners in maintaining system reliability."

The total cost of power in 2011 was 7.16 cents per kilowatt hour (kWh), up from 6.52 cents/kWh in 2010. This cost includes the average weighted wholesale market price of 3.15 cents/kWh and the average Global Adjustment of 4.01 cents/kWh (preliminary). 
Electricity trading activity between Ontario and its interconnected markets slowed, leading to lower imports and exports. Imports fell to 3.91 TWh from 6.4 TWh, while exports dropped to 12.9 TWh from 15.2 TWh.