18-Month Outlook



The IESO regularly publishes an 18-Month Outlook, which presents the IESO's assessment of the reliability of the Ontario electricity system over the short term. This quarterly publication assesses whether the existing and proposed generation and transmission facilities are adequate to meet Ontario's needs.

Here is the most recent issue and related documents.

Winter 2017: January 2018 to June 2019 (Released December 12, 2017)

  • Ontario Demand Forecast issued semi-annually, this document provides more detail about the 18-month forecast of electricity demand for Ontario. (Released December 12, 2017)
  • Ontario Transmission System provides specific details on the transmission system, including the major internal transmission interfaces and interconnections with neighbouring jurisdictions. (Released December 12, 2017)
  • Methodology to Perform Long Term Assessments contains information regarding the methodology used to perform the demand forecast, resource adequacy assessments, and transmission adequacy assessments in this Outlook report. (Released December 12, 2017)

For earlier reports, including Ontario Reliability Outlook and 10-year Outlooks see the Document Library.

Submitting of 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 18-Month Outlook and other reliability assessments, see the Calendar for Submission of Reliability Assessments Information.

Related Information

Ontario Reserve Margin Requirements: 2017 - 2021 reports on the operational planning reserve requirements to meet the NPCC resource adequacy design criterion over a five-year window.