The Grid
South Australia’s grid demand fell to 57 MW on a Saturday afternoon
We wrote on 3 August about what a home battery does to the evening peak. The other half of the same AEMO report is about the middle of the day, and it is the more striking half. On Saturday 18 April, in the half hour to 1.30pm, everything South Australia’s grid had to supply came to 57 megawatts. That is a new record, and it is 64 per cent below the old one. Victoria set a record the same month. And the midday negative prices that rooftop solar became famous for are now getting both rarer and shallower.
Operational demand is the electricity the grid itself has to supply. It is what is left after rooftop solar has quietly served the houses it is bolted to. So when minimum operational demand falls, that is not the country using less power. It is rooftop solar covering more of the daytime load before the grid is asked for anything.
In the April to June quarter, two states set new lows.
| Region | Minimum | When | Change on the previous Q2 minimum |
|---|---|---|---|
| South Australia | 57 MW | Half hour to 1.30pm, Sat 18 April | Down 100 MW, or 64 per cent, from 157 MW |
| Victoria | 1,986 MW | Half hour to 1.30pm, Sat 4 April | Down 247 MW, or 11 per cent |
| Whole national market | 12,670 MW | Half hour to 1pm, Sun 19 April | Not a record; the quarter’s low point |
AEMO attributes both records to the same combination:
high distributed PV output, mild weather conditions, and relatively low underlying demand
during daytime hours
. Mild weather matters because nobody is running heating or cooling, so
the underlying load is small to begin with and solar has less to cover.
The 57 megawatt figure is worth sitting with. South Australia has about 1.8 million people. For that half hour, the entire state’s call on its grid was roughly what a single medium gas turbine produces. Everything else was being met behind the meter, on roofs.
The renewables peak went to 72.2 per cent
The same quarter set an all-time high for renewable and storage contribution across the
national market: a new all-time high of 72.2% achieved during the half-hour ending 1130 hrs
on 31 May 2026
, which AEMO records as 1.6 pp higher than the previous peak set in
November 2024
.
Two things about that are worth separating. It is an instantaneous half-hour peak, not an average, so it does not mean the grid ran on 72 per cent renewables for the quarter. And it includes storage, which is discharge from batteries that were themselves charged earlier. Neither qualification makes it less real; both stop it being read as more than it is.
The part that shows up on a bill: negative prices are fading
For several years the midday story has been negative wholesale prices, where so much solar is generating that the spot price goes below zero. That is still happening, but it changed shape this quarter in two ways at once.
They got shallower. Prices between minus $10 and zero per megawatt hour
accounted for 89% of all negative price intervals, up from 21% in Q2 2025
. So negative
prices are now overwhelmingly shallow ones rather than deep ones. The average spot price during
those intervals increased from -$20.1/MWh to -$4.8/MWh
.
And they got rarer. AEMO attributes that to battery charging soaking up
daytime surplus, noting that Battery charging growth overlaid stronger daytime operational
demand, leading to fewer negative price intervals
, and that the result was
a significantly flatter intraday price profile than in Q2 2025
.
AEMO also attributes the shallower prices to something outside the grid entirely: large-scale generation certificate prices fell to an average of about $3 a certificate from $20 a year earlier. Those certificates are part of what a renewable generator earns, and when they are cheap the generator has less reason to keep running at a deeply negative spot price.
What that means for a household
If you are on a flat retail tariff, none of this reaches you directly this quarter. Retail prices are set well ahead of the spot market and a flatter wholesale day does not move your rate by itself.
Where it does matter is if you have, or are considering, a plan that pays you differently at different times of day. The whole appeal of soaking up cheap midday power, whether into a battery, a hot water system or an EV, rests on the middle of the day staying cheap. This quarter is the first clear sign that the batteries already installed are competing for that same cheap window and flattening it. That does not make load shifting a bad idea, and a flatter profile is a healthier grid. It does mean the arithmetic is moving, and anyone sizing a battery on the assumption that midday power stays near free should watch the next few quarters rather than assume.
It is also the pressure sitting behind the machinery we wrote about on 31 July: the $128 million solar backstop exists to curtail rooftop solar during exactly the minimum-demand conditions this report has just recorded two new records for. Submissions on who pays for it closed on 21 August 2026.
How we sourced this
Every figure above is from AEMO’s Quarterly Energy Dynamics report for Q2 2026, which covers April to June 2026. We read the report itself rather than any summary of it, and the quoted phrases are AEMO’s words. The comparison of South Australia’s 57 MW to a single medium gas turbine is our own illustration and is not in the report.
What we have not done. Minimum operational demand records are half-hour snapshots in mild autumn conditions, not typical days, and they say nothing about what happens at the evening peak or in a heatwave. We have not modelled any bill: the observation about load shifting is about the direction of the wholesale profile, not a calculation for any tariff or household, and retail prices are set separately and well in advance. We have not audited AEMO’s attribution of the shallower negative prices to certificate prices and battery charging; that is the report’s explanation, reported as such. Figures in this report are taken from tables and text, and where a chart is the only source we have not used it, because text extraction from this document interleaves chart labels into sentences.
Sources
- Australian Energy Market Operator, Quarterly Energy Dynamics Q2 2026 (PDF, covering April to June 2026, read 4 August 2026): the South Australian and Victorian minimum operational demand records and their dates and changes, the NEM-wide quarterly minimum, AEMO’s attribution of both records to distributed PV output and mild weather, the 72.2 per cent renewable and storage all-time high and its comparison with November 2024, the shift in negative price magnitudes and the change in average negative spot price, the attribution to battery charging and to large-scale generation certificate prices, and the flatter intraday price profile.
- The Electric Household, Three NSW networks want about $128 million for the solar backstop: the curtailment machinery built for minimum-demand conditions, and the 21 August submission deadline.
Spotted an error, or read these numbers differently? Tell us and we will check it against the report and log the outcome here.