Supplementary Capacity

Invitation to Tender for Supplementary Capacity 2025-26 (now closed)

AEMO has identified a potential requirement to secure up to 142 MW of Supplementary Capacity (SC) over the period from 1 December 2025 to 1 April 2026. In accordance with clause 4.24 of the ESM Rules, AEMO is commencing the SC process for the 2025–26 Capacity Year.

• Tender submissions are invited for two types of SC Service:
  • Availability and Activation (A&A) Service provided by Registered Facilities and Unregistered Equipment
  • Activation-only (AO) Service provided by Unregistered Equipment only
• The maximum term of SC Contracts will be 121 days, commencing at 8AM on 1 December 2025 and ending at 8AM on 1 April 2026. Shorter contract terms may be entered into as required.
• SC for the 2025-26 Capacity Year can be activated during the Service Period from 4PM to 9PM AWST on a Trading Day for A&A and AO contracts. AEMO is seeking service duration of 5 hours with a minimum of 5 MW of capacity. Lower service durations and minimum service quantities may be considered at the discretion of AEMO.
• Under the AO service, AEMO is allowing voluntary activation for up to 3 hours before and after the Service Period, which are 1PM – 4PM and 9PM - 12AM AWST (under “Extended Service Period”). Tenders that are able to offer voluntary activation during the Extended Service Period will be reviewed favourably during the tender evaluation.
• In 2023-24 Capacity Year, AEMO activated SC for a total of 70 hours during the Service Period. For the upcoming 2025-26 Hot Season, AEMO does not expect to activate SC in excess of this amount.

Excluded TNIs

• The following Transmission Node Identifiers (TNIs) are excluded by AEMO solely for the purposes of SC 2025-26.

Note, this list is current as of 20 August 2025.

For further details, please see a copy of the Tender Guidelines below.

Submissions for Supplementary Capacity must be submitted via the VendorPanel by 12pm AWST on Monday 15 September 2025.

The key activities of the 2025-26 Supplementary Capacity tender are outlined below:

For assistance, please contact the WA Registration, Monitoring and Procurement team at [email protected]

Western Power enquiries must be directed to [email protected]

WEM Procedure

The WEM Procedure for Supplementary Capacity can be found here:  AEMO | WEM Procedures 

2024 - 25 Supplementary Capacity Tender process (now closed)

AEMO has identified a potential requirement to secure up to 285 MW of Supplementary Capacity over the 1 December 2024 to 1 April 2025 period. As such, AEMO is commencing the Supplementary Capacity process for the 2024-25 Capacity Year in accordance with Section 4.24 of the WEM Rules.

• Supplementary Capacity for the 2024-25 Capacity Year will be activated between the hours of 3:30PM and 8:30PM AWST, in blocks of no less than 2 hours and must provide at least 1 MW of supplementary capacity.
• The maximum term of Supplementary Capacity Contracts will be 121 days commencing 8am on 1 December 2024 and ending 8am on 1 April 2025, with shorter Supplementary Capacity Contracts entered into as required.
• In 2023-24, AEMO activated Supplementary Capacity for 70 hours during the Service Period. AEMO does not expect to activate Supplementary Capacity in excess of that.

Submissions are invited for two different types of Supplementary Capacity Service:

• Availability and Activation Service provided by Registered Facilities and Unregistered Equipment. This service is similar to the service provided in previous Supplementary Capacity tenders for 2022-23 and 2023-24.
• Activation-only Service provided by Unregistered Equipment only. This is a new service applicable to this tender.

For further details please see a copy of the tender guidelines below.

Submissions for Supplementary Capacity must be submitted via the VendorPanel by Thursday 5 September 2024 by 5.00pm AWST.  

AEMO hosted a stakeholder information session on Monday 12 August. The presentation can be found below:

For any queries regarding the tender please contact the WA Capacity Market Investment team at [email protected]. 

Western Power enquiries must be directed to [email protected] and cc  [email protected]. 

Key activities  

AEMO is progressing the Supplementary Capacity process with key activities outlined below: 

The WEM Procedure for Supplementary Capacity can be found here:  AEMO | WEM Procedures 

Supplementary Capacity 2024-25 Outcome

AEMO has concluded the formal tender and negotiation process for the 2024-25 Supplementary Capacity (SC) process.

AEMO contracted 217.70 MW of Supplementary Capacity for the 2024-25 Hot Season. For the purposes of clause 4.24.11B, AEMO must publish the following information for each Supplementary Capacity Contract:

Invitation to Tender for Supplementary Capacity – WEM (now closed)

The Australian Energy Market Operator (AEMO) procures Reserve Capacity each year to ensure that there is sufficient generation capacity in the South West Interconnected System (SWIS) during peak demand periods.

Several changes and risks to supply have been identified since the publication of the 2022 WEM Electricity Statement of Opportunities in June 2022. This includes project delays, a voluntary capacity reduction for Alcoa Wagerup, an expected increase in AEMO’s peak demand forecasts and an increase in contingency reserve to account for decreasing reliability in the SWIS. As such, AEMO commenced the steps to procure up to 326 MW of anticipated shortfall of capacity between 1 December 2023 to 1 April 2024 in line with clause 4.24 of the WEM Rules.

AEMO sought tenders from providers capable of generation or load reduction which met the requirements of Eligible Services in line with clause 4.24.3 of the WEM Rules. This service is to be provided no earlier than 1 December 2023 and is to conclude by 1 April 2024.

Each Eligible Service must be available during the hours of 3:30 PM to 8:30 PM AWST in blocks of no less than 2 hours and must provide at least 1 MW of supplementary capacity. AEMO may procure this service from one or more providers, following evaluation of the submissions in line with AEMO’s internal procurement policy.

AEMO hosted an industry forum covering the requirements of the SRC process for the 2023-24 Capacity Year on 4 August 2023.

The Eligible Service must be available to be activated (if required) over a period of no longer than 16 weeks commencing on or after 1 December 2023 and ending on or before 1 April 2024.

The maximum contract value per hour of availability that will be accepted by AEMO for any Supplementary Capacity Contract is $ 1,661.12 per MW per hour. The Supplementary Capacity is expected to be required for no more than 48 hours throughout the period. 

Outcome

On 7 March 2024, AEMO concluded the formal tender and negotiation process for the 2023-24 SRC. The table below presents the related Supplementary Capacity Contract details in accordance with Clause 4.24.11B of the WEM Rules.

For assistance, please contact the Reserve Capacity (WA) team at [email protected].

Western Power enquiries must be directed to [email protected] and cc [email protected].

Invitation to Tender for Supplementary Capacity – WEM

The Australian Energy Market Operator (AEMO) procures Reserve Capacity each year to ensure that there is sufficient generation capacity in the South West Interconnected System (SWIS) during peak demand periods.

Since the release of the 2022 WEM Electricity Statement of Opportunities, AEMO has identified a potential requirement to secure up to 174 MW between 1 December 2022 to 31 March 2023. The causes of this shortfall include the early retirement of the Kwinana Cogeneration Plant, an extended Forced Outage of Pinjar unit 10 until 30 April 2023, increase in AEMO’s peak demand forecasts, ongoing fuel supply limitations and project delays related to the 2022-23 Capacity Year. As such, AEMO is commencing the supplementary Reserve Capacity (SRC) process for the 2022-23 Capacity Year, in accordance with clause 4.24 of the Wholesale Electricity Market Rules.

AEMO is progressing the SRC process through an Invitation to Tender.

Invitation to Tender

AEMO is seeking tenders from providers capable of generation or load reduction which meet the requirements of Eligible Services in line with clause 4.24.3 of the WEM Rules. This service is to be provided no earlier than 1 December 2022 and is to conclude by 1 April 2023. Each Eligible Service must be available during the hours of 5:00 PM to 9:00 PM AWST in blocks of no less than 1 hour and must provide at least 1 MW of supplementary capacity. The maximum contract value per hour of availability is $2,380.23 per MW for any Supplementary Capacity Contract that AEMO will accept. A Maximum Availability Percentage (as defined in the WEM Procedure: Supplementary Reserve Capacity) of 7.4% applies. AEMO may procure this service from one or more providers, following evaluation of the submissions in line with AEMO’s internal procurement policy.

AEMO has published the Invitation to Tender on VendorPanel - https://www.vendorpanel.com.au/PublicTenders.aspx

It is requested that respondents complete and submit the Tender Form and Schedule 1 (both found in the Invitation to Tender) and the Vendor Pre-Qualification Questions as part of their submission.

Submissions must be made via the VendorPanel by 5:00 PM AWST by Friday, 21 October 2022.

Queries may be submitted via email to [email protected].

AEMO hosted an SRC industry forum on 3 October 2022 and presented details of the SRC tender process. The presentation is available below.