Planning and Forecasting

The quarterly Reliability Outlook presents Ontario’s demand forecast and associated drivers, resource adequacy projections and the assumptions that inform them, as well as an assessment of the province’s transmission assets. For the second and fourth calendar quarter releases, a companion update will be published alongside the Reliability Outlook that provides additional insights about the forecasts.

In addition to the Reliability Outlook and methodology, the IESO has made its Transfer Capability Assessment Methodology for the Near-Term Transmission Planning Horizon publicly available. The Ontario Transmission System document was consolidated with this Transfer Capability Assessment Methodology document. Operating limits previously documented in the Ontario Transmission System document are now available in the Reliability Outlook.

The IESO issues its Reliability Outlook each quarter. Here are the most recent issue and related documents.

• Q1 2026 Reliability Outlook (Released March 19, 2026)
• Q4 2025 Reliability Outlook winter update (Released December 18, 2025)
• Methodology to Perform the Reliability Outlook contains information regarding the methodology used to perform the demand forecast, resource adequacy assessments, and transmission adequacy assessments in this Reliability Outlook.
• Transfer Capability Assessment Methodology documents the methodology used for performing assessments of Transfer Capability of the Ontario Bulk Electric System for transmission planning studies. This methodology is in accordance with the North American Electric Reliability Corporation standard FAC-013-2. The IESO has also used this methodology for the transmission assessment beyond the first 18 months in the Reliability Outlook.

Previous Reliability Outlooks from December 2020 onward and related information can be found in the Document Library, under the Planning and Forecasts category.

For Reliability Outlooks and related information prior to December 2020, please contact customer.relations@ieso.ca and specify the document, year and quarter requested, and advise whether it needs to be provided in an accessible format.

Submitting Reliability Assessment Information

Market participants are required to provide information to the IESO to enable it to conduct reliability assessments. These submissions are required each calendar year.

For submission deadlines for input information for the Reliability Outlook and other reliability assessments, see the Calendar for Submission of Reliability Assessments Information.

Related Information

The IESO reports reserve margin requirements over a five-year window, as required by the Ontario Resource and Transmission Assessment Criteria, and are generally published in the Annual Planning Outlook.

Additional Planning and Forecasting documents, previously referenced on this page, can be obtained by contacting customer.relations@ieso.ca. These archived documents include – in addition to our Reliability Outlooks prior to December 2020 – 18-Month Outlooks; the Ontario Planning Outlook; 10-Year Outlook; Integrated Power System Plan; Long-Term Energy Plan; and Supply Mix Advice Report. Please allow a minimum of one business day for a response and advise whether the document(s) need to be provided in an accessible format.