Ancillary services causer pays 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 the contribution factors, as set out in clause 3.15.6A of the National Electricity Rules and detailed in the following causer pays 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 Service Market Causer Pays factors - application period 24 January 2021 to 20 February 2021

The dispatch intervals were discarded in the contribution factor calculation process for the sampling period 6 December 2020 to 3 January 2021 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 6 December 2020 to 3 January 2021 due to contingencies that caused the power system frequency to leave the normal operating frequency band are:

Mainland – 3 dispatch intervals
Tasmania – 135 dispatch intervals

All dispatch intervals in the period from 17 December 2020 1205hrs to 3 January 2021 0000hrs have been manually excluded from the contribution factor calculation process under clause 6.2(a)(ii) of the Regulation FCAS Contribution Factor Procedure, due to an issue with the determination of Frequency Indicator (FI). This issue is still being investigated, and is expected to require further periods to be excluded in subsequent calculations.

Documentation 2021

Documentation 2020

Documentation archive

Older archived files

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