Planning and Forecasting

Planning is essential to a reliable, sustainable electricity future. The IESO plans and prepares for Ontario's electricity needs by assessing electricity requirements for the power system of today and tomorrow as well as planning to ensure electricity will be available when and where it is needed. The responsibility includes broad engagement with individuals, organizations and institutions most impacted by our decisions. It is an iterative process that must consider short-, medium- and long-range electricity needs as well as impacts on cost, reliability, the environment and others.

Dedicated planning processes exist for specific timelines and geographical areas (local, regional or provincial). These timelines are:

  • Near real-time forecasts
  • 18-months ahead
  • Long-term outlook

Near Real-Time: Days Ahead and Current Day Forecasts

Balancing Ontario's electricity demand with supply is a process that repeats itself 24 hours a day, seven days a week, 365 days a year. The IESO continually produces forecasts of expected demand and available generation, for weeks and days ahead. These forecasts take into account:

  • the day of the week;
  • detailed weather forecasts;
  • historical demand;
  • embedded (or distribution-connected) generation;
  • system conditions; and
  • special events or holidays.

While these forecasts are highly accurate, the IESO's control room operators must respond to real-time conditions on the power system at all times, adjusting generation to meet demand on a five-minute basis.

IESO Control Room

Forecasting the Output of Variable Generation

The IESO uses centralized wind and solar forecasting that provides reliable day-ahead and hour ahead estimates of energy output from these generators. These forecasts help the IESO anticipate the output of variable generation and manage the entire system more efficiently.

Power Data

See the current day and next day’s forecast of Ontario demand in the Power Data section.

Looking 18-Months Forward

Every calendar quarter the IESO publishes an 18-Month Outlook, which reports on the adequacy and security of resources and transmission to meet Ontario's forecast demand during this period. To conduct its assessment, the IESO collects information from market participants such as plans for new or modified facilities and any planned outages over the study period.

This report is used by market participants and industry stakeholders to inform their business decisions and to help plan equipment outages to ensure the reliability of Ontario's electricity system, and coordination of maintenance plans for generation and transmission equipment.

Read more about the 18-Month Outlook and related forecast documents.

Long-Term Outlook

For the longer term, the IESO forecasts energy demand and identifies sustainable electricity solutions for Ontarians in the 18-month to 20-year timeframe. Planning for Ontario's future electricity happens at three levels:

  • Provincial system planning   
  • Regional system planning  
  • Local distribution system planning

The IESO leads the provincial and regional system planning and local distribution system planning is led by the LDCs. While these are separate planning processes, the outcome of one process will inform and influence the other plans. For example, regional planning considers the impact of the provincial plan and inputs from the LDCs based on their distribution system plan; the outcome of the regional plan will then influence the next iteration of the provincial and distribution plan.

Provincial System Planning

Provincial system planning identifies the mix of energy resources and determines how electricity flows throughout the province. It ensures the long-term adequacy and reliability of the province’s integrated power system.

Part of the IESO’s role in provincial system planning is to develop the Ontario Planning Outlook report, which is an objective 10-year review and 20-year outlook for Ontario’s electricity system. The most recent report released in 2016 considers system requirements associated with capacity, reliability, market and system operations, transmission and distribution. It concludes that Ontario is well-positioned to meet provincial needs until the mid-2020s, while continuing to adapt to significant change across the sector. Accelerated change is predicted for the decades ahead, and the 2016 report explores the opportunities provided by various technologies and distributed energy resources.

The Ontario Planning Outlook serves as an objective baseline for the Ministry of Energy and sector stakeholders to understand electricity demand and supply outlooks, and to inform the Ministry’s formal consultation process for the development of the Long-Term Energy Plan (LTEP). After the release of the LTEP, the IESO and the Ontario Energy Board will develop implementation plans based on the goals and objectives set in LTEP 2017.

Long-Term Energy Plan cover 

The most recent LTEP, Achieving Balance was released by the Ministry of Energy in 2013.

The LTEP takes a pragmatic approach designed to balance the following five principles:

  • cost-effectiveness;
  • reliability;
  • clean energy;
  • community engagement; and
  • an emphasis on conservation and demand management before building new generation.

Regional System Planning

A reliable source of electricity is essential to supporting community growth. Regional system planning divides Ontario into 21 regions based on the configuration of the power system. The IESO is responsible for creating integrated regional plans, looking individually at each area’s unique characteristics to ensure a reliable electricity supply to the regional level. With consideration to requirements in the provincial and local level, regional planning allows for a community-customized approach. The IESO regularly measures the levels of supply and demand to determine changing electricity needs, and if required, begins a process to develop customized solutions.

Find your region and get involved in its electricity plan.

Local Distribution System Planning

There are approximately 70 local distribution companies (LDCs) across the province. They forecast, plan and operate their own part of the distribution system to deliver electricity to homes and businesses in their territory. While there are separate processes for LDCs to forecast and plan, the regional plan considers the reliability needs at the local level as part of the regional planning process. The IESO works with LDCs in the regional planning process to ensure regional level infrastructure are able to meet both regional and local requirements for reliable delivery of power homes and businesses.

Regional planning infographic thumbnail image

Regional Electricity Planning Infographic: Learn how regional electricity planning is used to identify and meet regional needs, forming the link between provincial and local planning.