Yo-yo-ing of ‘Market Demand’ in South Australia – on Wednesday 10th December 2025

It was fitting, in a way:

• that the AEMO’s draft of the 2026 ISP landed this morning;
• and also that (I believe) we’re under a week away from the final version of the Nelson Review recommendations.

Both documents speak to the envisaged future challenges in the NEM related to this energy transition, whilst some of these challenges have already emerged and are growing – such as what happened in South Australia today, seen in this snapshot from NEMwatch at 17:05 (NEM time) on Wednesday 10th December 2025:

Pay particular attention to the ‘5min Demand’ chart, which has been filtered to show:

• Measured on the LHS axis, the ‘Market Demand’ in South Australia is the red line;
• Whilst NEM-wide ‘Market Demand’ is shown as the RHS axis.

Within the ‘Notifications’ widget in ez2view, we’ve had an alert set up for many months now, looking at large changes in demand.  These alerts have been pretty quiet in prior years – but now in 2025:

• we have seen a large escalation in the number of instances
• some of which we’ve written up and tagged as examples of ‘large changes in demand’.

Particularly today in South Australia, there were two instances where the change was larger than 200MW:

• which is a large scale, relative to the size of the South Australian region
• and would almost never have triggered

Today, we see that this triggered twice in the one day – captured in the alert images below (but the trend chart above in NEMwatch shows that they were by far the only see-saw in the ‘Market Demand’ shape:

1)  First there was a +211MW change in the 11:30 dispatch interval (NEM time):

2)  Second there was a +232MW change in the 17:05 dispatch interval (NEM time):

Whilst some may say “batteries are the Swiss Army knife” (albeit not a magic wand), perhaps we should be a little more systematic in really thinking through the implications of gyrating market demand.

Because we also note (and it’s not a coincidence) the weakness of mainland frequency in the 17:00 dispatch interval … which suggests:

• The machinations in South Australian cloud cover a factor:
  • Not just for rooftop PV and Market Demand
  • But presumably for Semi-Scheduled solar, as well.
• And quite likely in other locations as well.