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 has formally consolidated both rule change requests and is seeking 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.

The draft rule would amend the methodology in the National Electricity Rules (NER) for calculating the cumulative price when one or more regions have reached the cumulative price threshold (CPT). The draft rule is largely consistent with the rule change request received from Delta. The draft rule will use received prices, instead of dispatch prices, to calculate the cumulative price when the CPT is reached in a region to which electricity is being exported to. This aspect of the draft rule seeks to improve efficiency in market signals, which should improve certainty and investment signals for peaking generation.

In response to Snowy's rule change request, the draft rule would amend the NER to adjust the methodology for the calculation of the cumulative price when AEMO has suspended the market due to market stress. The draft rule retains the calculation methodology proposed by Snowy, combined with a suggestion from Shell Energy to differentiate between market suspensions caused by technological failures with AEMO's systems and other reasons for market suspensions, including market stress. We consider that differentiating between a market suspension caused by market stress or technological failures with AEMO's systems will result in a more efficient market outcome, as the cumulative price calculation methodology will be based on the situation that caused AEMO to suspend the market. 

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.

The AEMC will run this rule change in parallel with the ERC0374 - CPT calculation during administered scheduled pricing. This rule change was lodged by Snowy Hydro on 28 August 2023.

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.

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.

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 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.  

The AEMC has commenced its consideration of the requests, and this consultation paper is the first stage.