On Tuesday 26th August 2026, the AEMO released the 2026 ESOO.  Following from this, we’ve already written three articles:

1)  Just about the release itself …

… we wrote that the ‘AEMO releases 2026 ESOO on Tuesday 25th August 2026’:

2)  Some of our own thinking, as we begin to crack the cover and explore

(a)  Firstly via ‘The grand ESOO Switch-a-Roo continues in 2026 … but hasn’t that approach jumped the shark?’. on the day of release;

(b)  And then some more context in ‘*Why* the ‘switch-a-roo with the ESOO’?’.

It’s quite a topical question (that we’ve contributed to recently), so I thought I would have a look at what is noted within the ESOO about the looming closure of Yallourn*.  That’s the focus of this article – which is aimed to be a faithful representation of what AEMO notes about the closure (we’ll continue our own analysis separately in follow-on articles).

* I did see on LinkedIn here that Thomas MacDonald from Baringa added, following (and with respect to the release of) the release of the 2026 ESOO:

‘Yallourn can – and should – retire in 2028 without impacting system adequacy. I don’t see a case in here to argue for its extension.’

A simple word count

Perhaps I was a little surprised, but searching the PDF for ‘Yallourn’ only triggers 9 entries … including some being more rudimentary:

• one being in Table 9 ‘Announced generator retirements across the NEM’ on p57/124 … indeed, that’s the first entry.
• and also general notes (4 references on p72)

So it’s the other 4 entries that we will cover in more detail below.

Speaking about Reliability

On Page 73/124 is an paragraph as follows:

‘Maintaining reliability to 2030

Despite the volume of retirements of large coal generators in the near term, expected USE remains within the reliability standard immediately following these closures. There is an additional 2.3 GW of anticipated and committed generation expected to be operational prior to the closure of Yallourn W (1.6 GW) in Victoria, 6.3 GW in New South Wales prior to the closure of Eraring (2.9 GW), and a further 3.8 GW in Queensland prior to the closure of Gladstone (1.7 GW). Much of this is VRE generation that will offset the loss of energy generation from the coal generators that have supplied much of the NEM’s electricity over their operating lives. With these new generation resources, supplemented by storage solutions, reliability gaps do not emerge within the T-3 horizon of the RRO (2029-30). ’

… so key questions for us to delve into later:

• What are these Projects?
• Remembering ‘the Switch-a-roo with the ESOO’, what’s the split between:
  • fully Committed
  • and only Anticipated?
• On the other dimension:
  • How much is ‘Anytime/Anywhere Energy’
  • and how much is Shaping and/or Firming?

Final reference of the 9 is on p115/124 in section ‘6.5 Regional insights for Victoria’ as follows:

Readers will note that the Unserved Energy results presented from the two main scenarios the AEMO presented in the document mapped with what we noted here as follows:

• The AEMO scenario ‘Government Schemes and Actionable Developments’ we described (in the 3rd row in the first table here) as ‘Second order sensitivity’;
• The AEMO scenario ‘Committed and Anticipated Developments’ we described (in the 2nd row in the first table here) as ‘First order sensitivity’;

After the trend of modelled results for ‘Resource Adequacy’ there were also trends for:

• ‘Electricity consumption trends’ and ‘Maximum demand forecast’ on p116
• ‘Minimum demand forecast’ on p117 at the top

… but none of them speak directly to Yallourn and system reliability.  Worth copying in (below):

• the ‘Generation and Storage developments’ trend at the bottom of p117; and
• ‘Supply scarcity risks’ at the top of p118 as follows;
• and the chart at the bottom of page 118 (not copied in fully here) notes that:

‘Supply scarcity risks increase in winter as heating loads are forecast to electrify. As coal-fired generators retire and demand grows, the surplus of dispatchable energy is expected to reduce. Supply scarcity risks are therefore increasingly likely to emerge during the shoulder season. In addition, supply will have greater exposure to weather variation in winter months, when solar generation is lower.’

Whilst the fact that supply scarcity risk increases in winter should not be a surprise to most readers, the key observation that jumps out to me in the chart is that FY 2028-29 is the year in which there’s a dramatic reversal in pattern:

• In FY 2027-28 the modelled percent of USE is 100% in summer;
• Whereas:
  • FY 2028-29 the modelled percent of USE flips to be ~80% winter and 20% summer
  • Which, of course, is a change triggered by the slated closure of Yallourn on 1st July 2028 (i.e. it’s not just the move to electrify heating).

Underneath this (and not shown at all in the image above) is a chart that’s featured in recent ESOO releases that shows the distribution of USE events by duration.

About Essential System Services to manage, after Yallourn closure

In our GRC2018 and GenInsights21 we wrote about ‘the schism’ and highlighted the role of ‘Keeping the Lights on Services’ still supplied by coal (and other units).

• Since that time we’ve also made comments about how prior issues of the ESOO might have been misinterpreted by some readers as ‘the whole story’
• So it’s great to see that, towards the end of the ESOO this year (from 92/124):
  • the AEMO includes the section ‘5.3 Maintaining system security is critical to power system operations’ that provides a summary
  • and, on p93/124, includes ‘Table 20 Summary of network requirements, to be addressed by transmission network service providers, as calculated for, and presented in, the 2025 Transition Plan for System Security’

At the bottom of the table is this focus on Victoria (and the closure of Yallourn, with 2 mentions):

So there are some other things to keep an eye on (not just energy and capacity) with respect to the ‘risks of Yallourn closing’ question.