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 Forward

Every calendar quarter the IESO publishes the IESO Reliability Outlook (formerly known as the 18-Month Outlook), which reports on the adequacy and security of resources and transmission to meet Ontario's forecast demand. The summer (June) and winter (December) versions look five years forward, while the spring (March) and fall (September) versions look 18 months forward. 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 Reliability Outlook and related forecast documents.

Long-Term Outlook

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 Local Distribution Companies (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 iterations of the provincial and distribution plan.

Provincial System Planning

Provincial system planning focuses on the electricity resources that transmit the energy from the generation source to local distribution companies across the province. The IESO’s bulk system planning processes address provincial electricity needs and consider the impacts of various factors on the electricity system, including policy directions, the supply/demand balance, operability requirements and others.

Annual Planning Outlook - coverThe IESO’s Annual Planning Outlook (APO) provides a 20-year forecast for Ontario's electricity system. The outlook includes projected electricity demand, a resource adequacy assessment, transmission considerations, and performance indicators, such as an emissions outlook. It also identifies the province's energy and capacity needs. By providing timely and transparent information about future electricity needs on a regular basis, the outlook is intended to guide investment decisions and market development.




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. Where there are regional system needs, the IESO is responsible for creating Integrated Regional Resource Plans (IRRPs), 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 more than 60 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 to homes and businesses.

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