The AESO is proposing an amendment to the definition of “inflexible block” set out in the Consolidated Authoritative Document Glossary (“CADG”) of the ISO rules. This definition relates to Section 202.3 of the ISO rules, Issuing Dispatches for Equal Prices, Section 202.5 of the ISO rules, Supply Surplus, Section 203.1 of the ISO rules, Offers and Bids for Energy, and Section 203.2 of the ISO rules, Issuing Dispatches for Energy.

The definition of “inflexible block” set out in the CADG currently does not explicitly restrict the indication of an inflexible block to be due to a physical constraint or operating constraint.

The AESO is proposing to amend the “inflexible block” definition to be subject to a physical or operating constraint, to appropriately restrict the indication of inflexible blocks solely for operational reasons, rather than commercial or other reasons. This will align the CADG and submission requirements set out in Section 203.1 with the language of Information Document #2012-008R, Energy Offers and Bids.

The amendment will also expand the applicability of inflexible blocks to bids such that an operating block in a bid may be designated as inflexible if it is associated with a physical constraint or operating constraint. This will accommodate the entry of large load projects into the market, which may need to indicate an inflexible block in a bid due to operational reasons.

The AESO has posted:

• A slide deck providing an overview of the background and motivation for the proposed amendment to the “inflexible block” definition;
• The Letter of Notice for development of the proposed amendment to the “inflexible block” definition; and
• Blackline and clean copies of the proposed amended “inflexible block” definition.
  
  

The AESO recognizes that stakeholders require information and context in order to provide meaningful feedback on the proposed amended “inflexible block” definition. To support stakeholders, we plan to do the following:

• On April 24, 2026, the AESO will post a blacklined and clean copy of the proposed amended “inflexible block” definition for written comments.
  • The AESO will provide Stakeholders an opportunity to provide written feedback on the proposed amended “inflexible block” definition with comments due on May 19, 2026;
• The AESO will review stakeholder feedback and consider revisions to the proposed amended “inflexible block” definition.
• On May 25, 2026, the AESO will post all written comments from Stakeholders;
• On May 29, 2026, the AESO will post written responses to all Stakeholder comments;
• Additional engagement with stakeholders may be scheduled if the AESO requires additional information or clarity; and
• In June 2026, the AESO will submit an application to the Alberta Utilities Commission for approval of the proposed amended “inflexible block” definition.