Ontario's Energy Capacity

Over the past decade, wind, solar, bioenergy, hydro, refurbished nuclear and natural gas-fired resources have replaced Ontario’s coal fleet. These resources, together with investments in conservation, demand response and transmission have reduced greenhouse gas emissions in Ontario’s electricity sector by more than 80 per cent.

The current installed capacity on Ontario’s transmission grid is approximately 38,079 MW. In addition to transmission-connected generation, there is currently more than 3,400 MW of generation capacity within Ontario’s local distribution systems. The largest percentage of distributed generation, also known as embedded generation, is from solar facilities.

Current installed capacity - transmission system

This chart shows Ontario’s current installed energy capacity by fuel type on Ontario's transmission system, as reported in the most recent Reliability Outlook, released June 2021. These figures do not include the capacity of embedded generators that operate within local distribution systems, except those that are registered to participate in Ontario’s wholesale electricity market.

Ontario's current supply mix from the Reliability Outlook

Source: Reliability Outlook, released September 2021, updated quarterly.

Current installed capacity - distribution system

This chart shows the amount of energy by fuel type that is in commercial operation on Ontario's distribution systems, as of  December 2020. This is also referred to as current installed embedded generation.

Piechart of Supply Mix on Distribution System

Percentages may not add up to 100 due to rounding.
Source: Progress Report on Contracted Electricity Supply, Third Quarter 2020.

For previous Contracted Electricity Supply Reports (2007-2019), please contact Contract Management at contract.management@ieso.ca and specify the year and quarter requested, and advise whether it needs to be provided in an accessible format.

Interested in how much energy is currently being produced by Ontario’s energy resources? The IESO publishes hourly generation output by fuel type. See Power Data for real-time data.

Planning for Ontario’s future energy capacity

The IESO has ensured that Ontario’s long-term electricity needs could be met by contracting for energy from diverse resources such as wind, solar, hydro, bioenergy, nuclear and natural gas. Energy was contracted from a wide variety of suppliers including private sector businesses, cooperatives, public sector organizations, Indigenous communities, community groups, school boards, farmers and homeowners.

Now that Ontario is experiencing a strong supply situation, the IESO is to working with industry stakeholders to introduce changes to Ontario’s energy markets that will allow for market-based opportunities for investment and participation through capacity auctions. Capacity auctions offer greater flexibility to address changing system needs in shorter time frames – three and five year periods – and at the lowest cost to consumers.


Read how the IESO is working with stakeholders to evolve the electricity market, enhance its electricity market design to improve market efficiency and unlock future opportunities.