We have captured below some key questions that participants and prospective providers of ancillary services have asked about our processes and different ancillary services the System Operator procures. Use ctrl+F if you have a key word you are looking for. Otherwise, we have a section for general questions, and then the rest are divided by ancillary service. If you have questions that aren’t answered below, please reach out to [email protected].
General
Q: I am a provider of an ancillary service. Where can I find more information about what I am required to do?
A: Our About Ancillary Services webpage has general information for providers. You can also refer to our Procurement Process webpage, your ancillary services contract, and the Procurement Plan. Keep your Code obligations in mind as well.
Q: What is the status of the new (as of 2026) Emergency Reserve ancillary service?
A: We provide updates about this on our Emergency Reserve Scheme webpage.
Q: Where can I find reporting on the System Operator’s procurement of ancillary services?
A: A list of current providers can be found on this webpage. Information on the cost of ancillary services procured can be found in our quarterly performance reports.
Q: Are there any ramp rate considerations that inverter-based asset owners must consider when providing ancillary services?
A: Inverter-connected assets without mechanical constraints can change their output very quickly compared to other conventional generation. When the capacity of generating stations using inverter-connected assets rises to a point where fast ramping may affect the ability of the system operator to meet its Principal Performance Obligations, ramp rate constraints may be placed on the rate of change of output to avoid this. Each generation station and unit will be assessed on a case-by-case basis by the System Operator to determine if any ramp rate restrictions need to be applied for changes in loading during normal operation. The technical requirements are outlined in the Ancillary Services Procurement Plan.
Q: Should asset owners comply with AS/NZS 4777.2:2020?
A: The System Operator advises asset owners to install inverter-connected assets which are compliant with AS/NZS 4777.2:2020 to ensure consistent operation of these assets across the system. However, we recognise that there are differences in performance characteristics between Part 8 Code asset owner performance obligations (AOPOs) and this standard. Where an asset owner has a Code obligation and there is a difference between the AOPOs and this standard, the Code takes precedence.
Q: Is bidding required for battery energy storage systems (BESS)?
A: BESS may be classified as a direct consumer if the BESS has a point of connection to the Grid, as they draw load from the Grid to charge. Bids will be required for load connected at a non-conforming Grid Exit Point (GXP). If the charging load is a significant portion of total load at a GXP, the GXP may be re-classified as non-conforming. The Authority classifies GXPs as either conforming or non-conforming and may consider a reclassification application. Bids are supplied through the Wholesale Information Trading System (WITS), in a similar way to generator offers.
Q: Can BESS provide interruptible load and dispatchable demand?
A: BESS may provide interruptible load and dispatchable demand. Dispatchable demand and interruptible load are co-optimised within the market solver. However, BESS injection and offtake are not co-optimised. Therefore, participants must validate their bids and offers to avoid situations where they could be scheduled to both inject and consume load at the same time.
BESS with less than 10 MW capacity may also apply for approval from the System Operator to be a Dispatch Notified Load (DNL). This is a lower-compliance version of dispatchable demand, equivalent to the distinction between ‘full’ generation and DNG.
Note: a BESS that is classified as a Dispatched Notified Generation (DNG) and/or DNL may not offer ancillary services.
Q: Do providers need to account for both the injection and offtake sides of the BESS?
A: The asset owner is accountable for ensuring the reserve offers from an inverter connected device are as accurate as practicable, which for BESS will be subject to energy capacity and residual state of charge for each trading period.
Frequency Keeping
Q: Can inverter-connected assets offer frequency keeping?
A: Inverter-connected assets may provide frequency keeping (either multiple frequency keeping (MFK) or single frequency keeping (SFK)). Under current (2026) market arrangements, BESS may only offer frequency keeping when it is generating, and the minimum offer for frequency keeping is 4 MW. Owners of inverter-connected assets must ensure they have a sufficient primary energy source or stored capacity to maintain this frequency for at least a 30-minute trading period.
Instantaneous Reserve
Q: How does the System Operator determine that data for analysis of performance is required from interruptible load providers in response to an under-frequency event?
A: The System Operator will assess the performance of interruptible load (IL) providers in under-frequency events in which they were required to respond. Generally, this will be when the frequency has dropped below 49.20 Hz for longer than 200 ms. However, we note that an under-frequency event occurs when the grid frequency falls below 49.25 Hz as per the Code definition, so IL providers should plan to be able to provide data for any event in which the grid frequency falls below 49.25 Hz.
Q: I am interested in providing instantaneous reserve; how should I get started?
A: Familiarise yourself with the activities identified on our Procurement Process webpage. Please contact us at [email protected] if you have specific questions that are not answered there.