Skip Links
Powering Tomorrow > Summer Reliability 2021
Electricity 101

Summer Reliability 2021

July 16, 2021  |  Article

The latest Reliability Outlook is here, and it shows Ontario is well-positioned for summer. Let’s take a look at how the sunny season impacts the electricity grid and what to expect over the coming months. 

IESO Summer Reliability 2021

A diverse supply of resources will contribute to grid reliability this summer, including capacity auction participants that will provide demand response, imports, generation and energy storage.

The IESO Capacity Auction secured close to 1,000 MW of capacity for the Summer 2021 period.

Large industrial customers will also be supporting grid reliability this summer, through the Industrial Conservation Initiative (ICI). Industrial customers will help reduce peaks by curtailing their energy use during peak hours. In 2019 ICI helped reduce demand by ~1,600 MW.

To prepare for the summer season, the IESO implements readiness processes and procedures, including:

  • Testing generation units for readiness
  • Testing capacity auction resources
  • Coordinating outage plans with generators, transmitters, neighbouring areas, and gas operators

The summer forecast is calling for above normal temperatures. Under normal weather conditions the forecasted peak for the summer is 22,500 MW – and more than 24,500 MW under extreme weather conditions. During a prolonged heatwave in 2020, Ontario’s demand reached 24,446 MW. 

Summer is the season when demand is the highest in Ontario, primarily due to air conditioning load. On hot summer days, air conditioning can account for one-third of Ontario’s electricity use.

See how your air conditioner can work more efficiently this season

Air conditioning load can make up one third of Ontario's electricity use on hot days

Weather has always been the largest influencer of demand, and during the pandemic demand has become more weather-sensitive due to the number of Ontarians working from home. Check out how summer weather can influence demand.

Humidity can add up to 3,000 MW due to increased A/C load. Cloud cover can reduce demand by up to 1, 000 MW. Transmission lines heat up as the flow of power increases, limiting how much power can be transferred. Wind can cool the lines and increase power flows. Each degree about 16 C raises demand by 150 MW

Although energy demand in most sectors has returned to pre-COVID levels, there will be some impact on demand as businesses begin to safely re-open. The IESO is well-positioned to support the re-opening this summer.

Read the Reliability Outlook