The ISO is seeking proposals for the provision of Essential System Services (ESS) in the North-West Interconnected System (NWIS).
The ISO invites providers to submit proposals to submissions@pilbaraisoco.com.au by 5pm Friday 16 October 2026.
Background
On 7 July 2026 the ISO published a consultation paper outlining the proposed methodology that would be followed when undertaking ESS studies in the NWIS to inform procurement of SRESS for 2026-27.
The paper sought submissions on:
- the proposed assumptions and methodology to study SRESS requirements, including load levels, load inertia, load relief, generator headroom modelling, generator SPRINT modelling, and credible dispatch cases; and
- the proposed approach to manage credible contingency sizes for the purposes of procuring ESS.
The ISO received several submissions on the ESS Studies Consultation Paper, which have been incorporated into the ESS studies approach. The ISO will publish submissions and public responses in the coming weeks.
The ISO is seeking proposals for provision of ESS for the period of 1 December 2026 to 30 November 2027, with an option to extend contracts by a further 12 months.
The ISO will be consulting on the ESS procurement decisions using at least the Expedited Consultation Process outlined in Appendix 1 of the Rules. The indicative procurement and consultation process timeline is as follows*:
| Event | Date | Status |
|---|---|---|
| Publish consultation paper and invitation for submissions | 7 July 2026 | Complete |
| Public submission period | 7 July – 21 July 2026 | Complete |
| Publish responses to stakeholder submissions and final ESS studies methodology | October 2026 | In Progress |
| Seek proposals for ESS | 24 September – 16 October 2026 | In Progress |
| Consultation on Draft Decision for ESS | October 2026 – November 2026 | Not started |
| Final Decision on ESS | November 2026 | Not started |
Documents related to this proposal
Request for Proposal – Essential System Services 2026-27
Proposed ESS Contract 2026-27 – FCESS and Base SRESS