AEPC_2025_15 Supplementary Capacity

The consultation process

The consultation process is now closed. Relevant dates are outlined below.

Procedure change proposal

Electricity System and Market Rules – Clause 2.10

Date of Notice: 5 September 2025

Matter under consultation

AEMO commenced the Procedure Change Process to propose amendments to the WEM Procedure: Supplementary Capacity (Procedure) in accordance with AEMO’s obligations under the Wholesale Electricity Market Amendment (RCM Sequencing) Rules 2025 (Amending Rules) which commence on 1 January 2026.

The Amending Rules extend the requirements for Supplementary Capacity to include Flexible Capacity.

AEMO proposed the following amendments to the Procedure to ensure consistency with the Amending Rules: :

• table 3 is amended to prescribe the information that must be provided to Western Power (unless agreed otherwise) when a Potential Provider seeks assistance or assessment from Western Power in relation to the provision of Supplementary Capacity for Flexible Capacity services; and
• paragraph 3.2.1 and 3.2.2 are amended to extend section 3 to Flexible Capacity services.

In addition, AEMO has undertaken minor amendments of an editorial nature to improve clarity, correct typographical errors and align with AEMO’s modern WEM Procedure templates.

On 6 February 2025 the State Electricity Objective (SEO) replaced the Wholesale Market Objectives under section 3A of the Electricity Industry Act 2004 and clause 1.2.1 of the ESM Rules.

AEMO considered the Procedure is consistent with the SEO as it relates to:

• Power System Security and Power System Reliability outcomes, noting that the Supplementary Capacity mechanism is designed to procure capacity where a shortfall is forecast in order to maintain Power System Security and Power System Reliability;
• electricity pricing outcomes, noting that the Procedure gives effect to requirements under the ESM Rules that relate to the achievement of the required services under a competitive process, and assists with bringing new generation to market that in-turn reduces the potential for future procurement of Supplementary Capacity; and
• the environment, noting that, to the extent permitted under the ESM Rules, the Procedure is technology agnostic, allowing for participation by low emissions technologies.

Invitation to make submissions

AEMO invited written submissions on this Procedure Change Proposal, including any alternative or additional proposals that may improve the Procedure or better meet the State Electricity Objective under section 3A of the Electricity Industry Act 2004 and clause 1.2.1 of the ESM Rules.

AEMO requested that respondents identify any parts of their submission that they wished to remain confidential, explaining why. AEMO advised that it may still publish that information if it does not consider it to be confidential, but will consult with the respondent before doing so.

When making a claim for confidentiality, AEMO encouraged respondents to familiarise themselves with Chapter 10 of the ESM Rules, which imposes obligations in respect to the release of documents. 

Meetings

AEMO advised that, before the closing date for submissions, any person may request a meeting with AEMO to discuss the issues and proposed changes raised in the Procedure Change Proposal, stating why they consider a meeting is necessary or desirable.

If appropriate, meetings may be held jointly with other stakeholders.

Subject to confidentiality restrictions, AEMO generally makes details of matters discussed at meetings available to other stakeholders as part of the final published Procedure Change Report (or earlier, where applicable).

Closing date and time

AEMO advised that submissions in response to this Procedure Change Proposal should be sent by email to [email protected], to reach AEMO by 5.00 pm (AWST) on 7 October 2025.

AEMO advised that all submissions must be in electronic format (pdf or Microsoft Word) and should use the Procedure Change Submission form.

AEMO noted that it is not obliged to consider submissions received after the closing date and time, and that any late submissions should explain the reason for delay and the detriment expected if AEMO does not consider the late submission.

Publication

AEMO advised that all submissions will be published on AEMO’s website and that confidential information will not be published, other than as specified above. 

Submissions

There were no submissions.