Ontario’s Electricity System – Frequently Asked Questions

How much of Ontario’s electricity comes from nuclear power? Hydroelectricity? Solar, wind, coal, gas, bio?

Based on a combination of IESO data, electricity generation in 2015 was provided by:

  • nuclear 60%
  • hydroelectric 24%
  • natural gas 10%
  • wind 6%
  • solar <1%
  • bioenergy <1%

Why is energy conservation treated the same as other generation sources when you look at electricity production in Ontario?

Ontario has committed to ensuring conservation is the first resource considered before building new generation and transmission facilities and will be the preferred choice wherever cost-effective. Conservation is the cleanest and most cost-effective energy resource and it offers consumers a way to reduce their electricity bills.

Conservation is not treated the same as other generation sources. Conservation reduces demand for electricity on Ontario’s grid which in turn reduces the need to build more expensive generation and transmission facilities. Reductions in electricity demand are achieved in a number of ways, including energy efficiency, demand management (e.g., time-of-use pricing), behavioural changes and load displacement.

The 2013 Long-Term Energy Plan includes charts showing Ontario’s total forecast energy production in 2013 and 2032 which, for comparative purposes, show the amount of generation that is expected to be avoided as a result of conservation (see 2013 LTEP footnotes, page 24).

How does the province know how much electricity is needed at any given time of the day?

Each day, the Independent Electricity System Operator (IESO) forecasts supply and demand for the following day, and up to a month ahead. Forecasted demand is posted online so that generators can anticipate how much electricity will be required. The IESO’s day-ahead forecasts are highly accurate and typically differ by less than 2% from the actual demand figures.

The IESO also monitors and balances the system in real-time. The IESO collects bids and offers from generators until two hours before the electricity is needed. The IESO then matches the offers from generators against forecasted demand, and instructs the generators to provide electricity to the grid starting with the lowest cost bids first and proceeding to the next cheapest until demand is satisfied.

Longer-term forecasts help the IESO assess whether there will be adequate generation to meet demand needs on a quarterly basis – these assessments are published as the 18-Month Outlook.

What are the largest consumers of electricity in Ontario and why?

According to the IESO, there are approximately 300 large electricity consumers in Ontario. These large consumers are mainly large businesses and institutions. Large businesses, typically industrial consumers such as manufacturers and mines, run electricity-intensive machinery. Similarly, large institutions such as hospitals, also require electricity 24/7.

How much more electricity do we use today than we did 100 years ago? And why is that?

Electricity first came to Toronto in the late 1880s. In 1908, Toronto citizens voted overwhelmingly to form a municipal electricity company. The official “turning on” ceremony, marking the beginning of Toronto Hydro-Electric System, took place at Old City Hall on May 2, 1911.

100 years ago, there were only a few thousand customers in the city of Toronto, despite a population of nearly 400,000. In total Toronto Hydro delivered 7 million kilowatt hours in the decade of the 1910s, the equivalent of about 70 of today’s residential consumers.

The price of electricity, adjusted for inflation, was considerably more expensive 100 years ago compared to today, and this accounts in part for the drastically lower usage. More importantly, electricity was a relatively new technology, and the generation, transmission and distribution infrastructure was only starting to be put in place at the time.

What unit is electricity measured in?

Kilowatts (kW) are a common measure of electrical power, equal to 1,000 watts. Megawatts (MW) are another common measure of electrical power. One megawatt is equal to one million watts.

A standard unit for measuring electrical energy produced or consumed over time is the kilowatt hour (kWh). One kWh is the amount of electricity consumed by ten 100-watt light bulbs burning for one hour.

Are wind farms and solar farms the same as a power plant? If not, how are they different?

Renewable is different because once renewable generation facilities are built, the fuel is free and does not generate greenhouse gases or harmful pollutants. Wind turbines capture the kinetic (moving) energy in the wind and convert it to electricity. The energy of the wind causes the turbine blades to rotate, which turns a shaft that moves magnets in the generator, thereby creating electricity.

There are approximately 1,500 wind turbines in Ontario, which have the capacity to generate more than 2,700 megawatts (MW) of electrical power. These wind energy projects are expected to produce enough electricity each year to power more than 750,000 homes.

Wind energy projects are located in various parts of Ontario, particularly in places that have stronger winds. A number of wind projects are located near the shores of Lake Huron and Lake Erie.

Solar photovoltaic (PV) technology converts the sun’s rays into electricity. Light from the sun stimulates electrons in the solar PV semiconductor material and creates a flow of electricity. Even on cloudy days, solar PV systems can still produce some electricity.

There are more than 3 million solar PV modules installed in Ontario, which all together can generate 1,100 MW, or enough electricity to power more than 140,000 homes per year. Solar PV modules can be found in large-scale ground mounted solar farms in rural areas, as well as on residential and commercial building rooftops all across the province.

Why are we being encouraged to conserve electricity?

Conservation reduces the need to build new generation and transmission facilities, which helps mitigate electricity rate increases. Conservation is also the cleanest and most cost-effective energy resource and it offers consumers a way to reduce their electricity bills.

Where are Ontario’s power plants located? How would I recognize what they look like?

Ontario produces power from a wide variety of generation types (e.g. nuclear, hydro, solar, wind, natural gas and biofuels). These power plants are located all across the province and are the backbone of Ontario’s clean, reliable and affordable supply of electricity.

Some sources of generation, for example wind, use infrastructure which make sites easily recognizable as power plants (see below for a picture of a wind farm in the region of Algoma). However, the buildings and infrastructure used for other types of generation, such as natural gas and nuclear, may look like typical industrial facilities and so are less recognizable as power plants (see below for a picture of a natural gas generating facility in St. Clair Township, and the Bruce Nuclear facility near Tiverton.)

An interactive map illustrating the location of Ontario’s largest power plants can be found on the Independent Electricity System Operator’s (IESO) website

Turbines Looking  Toward Goulais Bay

Prince I Wind Power Project (99 MW) is a wind farm located in the townships of Aweres, Dennis, Pennefather and Prince.
Source: IESO website

St.Clair Energy Centre COD March 30,2009

St Clair Energy Centre (577 MW) is a natural gas generation facility located in St. Clair Township, Ontario.
Source: IESO website

Bruce Nuclear Facility

Bruce Nuclear Facility (6,610 MW) is a nuclear power plant located on Lake Huron in Tiverton, Ontario.
Source: IESO website