The Coordinator of Energy (Coordinator) is conducting a review of the Essential System Services (ESS) Framework (the Review), incorporating:
- a review of the ESS Process and Standards under Section 3.15 of the Electricity System and Market (ESM) Rules; and
- a review of the Supplementary Essential System Services Procurement Mechanism (SESSM) under clause 2.2D.(h).
The review of the ESS Process and Standards and the basis for setting the ESS requirements aims to assess whether the existing framework is effective to ensure power system security and reliability can be maintained as the energy transition continues.
There are three types of ESS in the WEM. However, only the Frequency Co-optimised Essential System Services (FCESS) are being considered as part of this Review.
Section 3.15 of the ESM Rules requires the Coordinator to complete the first review of the ESS Process and Standards within two and half years of new WEM commencement. This review can be carried out earlier if necessary. In this instance, the Review will be commenced early, due to:
- the transitional arrangements requiring all registered Facilities accredited for FCESS to offer their full accredited capability ending on the 1 April 2024;
- AEMO has not yet finalised several key procedures that support the ESS Framework, including the WEM Procedure relating the Low Reserve Conditions (describing how AEMO assesses the probability of accredited ESS providers being insufficient to meet the ESS Standards) and two WEM Procedures relating to the SESSM Trigger;
- there have been persistent shortfalls in available FCESS since the start of the new WEM, which have led to high FCESS costs; and
- the total costs of ESS, including FCESS Uplift costs, have increased substantially, driven by significant costs increases for all FCESS Market Services.1
An ESS Framework Review Working Group (ESSFRWG) has been established by the Market Advisory Committee to support the Review. Energy Policy WA (EPWA) will provide administrative support to the ESSFRWG.
On the 10 November 2025, EPWA published a Consultation Paper that contains five proposed outcomes of the Review, including proposals for:
- AEMO to update and publish the technical and operational guidelines relating to FCESS quantification and dispatch processes:
- ESS Quantities WEM Procedure;
- Dynamic Frequency Control Model (DFCM) process
- Real Time Frequency Stability tool process; and
- Supplementary ESS Mechanism documentation.
- AEMO to review the inputs, parameters and assumptions for the DFCM and test whether they should be updated to reflect current system conditions and drive relevant and correct outputs.
- Increase the Rate of Change of Frequency (RoCoF) Safe Limit from 0.25 Hz per 0.5 seconds to 0.75 Hz per second to reduce the need for AEMO interventions.
- AEMO to implement a monitoring program over a twelve-month period to track the amount of headroom available from unaccredited Facilities or non-dispatched FCESS Facilities to better quantify mandatory Primary Frequency Response (MPFR) availability to assess the level of Contingency Reserve Raise that could be provided from the inclusion of MPFR.
- Assess the suitability of synthetic inertia (RoCoF Control Service) from Battery Energy Storage Systems (BESS) in complementing synchronous Inertia from rotating machines, and consider potential barriers and suitable incentives for grid-forming BESS to provide such services.
EPWA has published for consultation an addendum - Exposure Draft of Electricity System and Market Amending Rules, to the Essential System Services Framework Review.
This addendum includes proposed ESM Amending Rules to increase the Rate of Change of Frequency Safe Limit from 0.25 Hz per 0.5 seconds to 0.75 Hz per second, to implement one of the proposed outcomes of the Review.
To review the proposed ESM Amending Rules, please refer to the addendum, by clicking the following link.
Stakeholders are invited to provide written feedback ESM Amending Rules Framework Consultation Paper, including the proposed ESM Amending Rules in the addendum, before 5:00pm (AWST) on 15 December 2025. Feedback can be sent to energymarkets@deed.wa.gov.au. Late submissions may not be considered.
Any submissions received will be made publicly available on this web page unless requested otherwise.
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