Following the publication of its draft determination 29 January 2026, the Commission has decided to make a more preferable final rule that amends the calculation of the cumulative price during periods of peak market stress in response to two rule change requests submitted by Delta Electricity (Delta) and Snowy Hydro (Snowy) that were subsequently consolidated.

Stakeholder feedback informed the final rule, and the Commission’s decision to make minor adjustments between the draft and final rule.

In response to Delta's rule change request and consistent with our draft determination, the final rule amends the NER so that received prices (instead of dispatch prices) are used to calculate when the cumulative price threshold (CPT) is reached in a region. This will improve efficiency in market signals, which will improve certainty and investment signals for peaking generation.

In response to Snowy’s rule change request, the final rule amends the NER to exclude market suspension pricing trading intervals from the cumulative price calculation. This improves the protection provided by the CPT following a market suspension where there was underlying market stress. Adjusting the CPT calculation methodology will also lower risks to generators selling hedging products and  enhance the protection to consumers provided by the administered price cap.

Informed by stakeholder feedback, the final rule includes minor consequential amendments to align the NER with AEMO's processes for applying market suspension pricing and its post-event reporting on a market suspension. This promotes transparency and consistency for good regulatory practice.

The final rule comes into effect 1 November 2028, to allow the Australian Energy Market Operator (AEMO) sufficient time to update relevant processes given its existing resourcing commitments.

Background

On 2 February 2023, the AEMC received a rule change request from Delta Electricity to amend the National Electricity Rules (NER).

Delta Electricity's rule change request proposes an amendment to the NER relating to the methodology for calculating the cumulative price threshold (CPT) when one or more regions have reached the CPT.

Snowy Hydro submitted a rule change request to the AEMC on 28 August 2023, proposing an amendment to the NER to suspend the calculation of the cumulative price when the administered scheduled pricing is used.

Both rule change requests were submitted following by the market event that occurred in winter 2022, which saw multiple regions exceed their cumulative price thresholds and the market was eventually suspended.

When a region is not under administered prices but is exporting electricity to a region that is under administered prices, the dispatch price is used for dispatch, but the settled price that is received by the generator is lower. This is because the dispatch price is capped at the APC and then scaled down. Delta Electricity considers that this approach creates an outcome where a region’s CPT is reached based on higher dispatch prices despite lower prices being received in settlement.

Snowy Hydro considers that an issue became apparent during the 2022 market event whereby if the market suspension is in place long enough and administered scheduled pricing is used, it results in the cumulative spot prices being below the CPT when administered scheduled pricing is removed. This can occur despite the market conditions that initially caused the breach of the CPT persisting. Snowy Hydro suggests this can lead to the immediate resumption of extreme spot prices, undermining the protection that the CPT was designed to provide.

Both rule change requests argue changes to the calculation of the cumulative price in specific situations, to better align it with the original policy intent of the market setting.  
On 16 October 2025, the AEMC published a consultation paper that covers the issues and proposed solutions contained in the rule change request from Delta Electricity and Snowy Hydro.Submissions closed on 20 November 2025.

The Commission published its draft determination on 29 January 2026, to make a more preferable draft rule to amend the calculation of the cumulative price during periods of peak market stress in response to two rule change requests submitted by Delta Electricity (Delta) and Snowy Hydro (Snowy).

The Commission formally consolidated both rule change requests and sought feedback from stakeholders on the more preferable draft rule (the 'draft rule'), including the expected magnitude of benefits and implementation costs, by 12 March 2026.