Ancillary services contribution factors

One of the features of the ancillary service market is that only the costs for frequency control regulation services are to be allocated in accordance with contribution factors determined for market participants, as set out in clause 3.15.6A of the National Electricity Rules and detailed in the following procedure.

Under the Rules, AEMO must update these contribution factors every four weeks, and publish the factors at least 10 business days prior to them being applied in the market.

The Rules also require AEMO to publish the historical data used to calculate these factors. This historical data is available here on the AEMO web site.

Final factors used in settlements may vary slightly from previously published values due to minor error corrections.

AEMO calculates contribution factors normalised according to region demand. 

Ancillary Services Contribution factors - application period 22 December 2024 to 18 January 2025

The dispatch intervals that were discarded in the contribution factor calculation process for the sampling period 3 November 2024 to 1 December 2024 for reasons other than the effect of contingencies and the data samples where FI and system frequency were mismatched, are listed in Exclusions List (pdf).

The number of dispatch intervals that were discarded in the contribution factor calculation process for the sampling period 3 November 2024 to 1 December 2024 due to contingencies that caused the power system frequency to leave the normal operating frequency band are:

Mainland – 7 dispatch intervals

Tasmania – 606 dispatch intervals

Documentation 2025

Documentation 2024

Documentation 2023

Documentation 2022

Documentation 2021

Documentation 2020

Documentation archive

Older archived files

For older documentation please contact the AEMO Information and Support Hub.