2025-26 Essential System Services Final Decision
The ISO has published its Final Decision for 2025-26 Essential System Services (ESS):
The ISO has entered into ESS contracts for the period of 1 December 2025 to 30 November 2026.
In accordance with Rule 200, on 3 November 2025 the ISO invited stakeholders to provide written responses on its 2025-26 Essential System Services Draft Decision.
The ISO received two submissions and has published its response to stakeholder submissions.
Stakeholder submissions can be found below.
Supplementary SRESS
Participants who are not contracted for Supplementary SRESS may apply to do so by submitting a proposed contract found using the proforma contract on the ISO’s website.
Background
On 30 May 2025, the ISO published the Annual Report into the Cost and Effectiveness of Essential System Services in 2024-25. Section 7.1 of this Report identified a key challenge in procuring ESS for the 2025-26 procurement cycle was the connection of new BESS facilities.
In August, the ISO published an ESS Issues Paper, seeking submissions on:
- The impact of the new BESS facilities on the system’s response to credible contingencies and the required headroom level;
- The procurement approach and mix of services; and
- Consideration of short-term measures and longer-term rule changes necessary for the ISO to meet the ESS objectives.
The ISO received several submissions on the ESS Issues Paper, which were incorporated into the ESS procurement approach. The ISO published responses to stakeholder feedback and an Update to the ESS Issues Paper.
The ISO sought proposals for the provision of ESS for the period 1 December 2025 to 30 November 2026.
With the Final Decision and execution of contracts, the ESS procurement process for the 2025-26 procurement cycle has now been completed.
| Event | Date | Status |
|---|---|---|
| ESS Issues Paper published | 29 August 2025 | Complete |
| Public submission period | 29 August – 19 September 2025 | Complete |
| ISO responses published | October 2025 | Complete |
| Seek proposals for ESS | 25 September – 17 October 2025 | Complete |
| Consultation on Draft Decision for ESS | 3 – 24 November 2025 | Complete |
| Final Decision on ESS | 28 November 2025 | Complete |
Documents related to this proposal
Notice: 2025-26 Essential System Services Final Decision
Notice: Invitation for submissions – 2025-26 Essential System Services Draft Decision
Clarification Register – RFP for NWIS Essential System Services 2025-26
Request for Proposal – Essential System Services
Annual Report into the Cost and Effectiveness of ESS in 2024-25
Submissions on Draft Decision
Submissions