The week of 16–23 August delivered a familiar mix for NEM watchers: comfortable renewable supply overnight and in shoulder periods, punctuated by sharp evening price spikes as thermal and interconnector limits bit. Average prices across the mainland NEM regions ranged from the high teens to the mid-$70s/MWh depending on the day, with Victoria and South Australia both dipping to single-digit or teen daily averages on 18 and 19 August amid strong wind output, before swinging back up into the $70–$100/MWh range later in the week as conditions tightened.
Tasmania was the standout region for volatility relative to its usual profile — hitting 100% renewable generation on multiple mornings while simultaneously recording some of the sharpest intraday price swings of the week, including a jump from around $30/MWh to over $90/MWh within a single settlement window on 21 August. This underlines a pattern we've flagged before: high renewable share and price stability are not the same thing, particularly when network constraints are binding.
The WEM told a different story, trending firmer than the NEM for most of the week, with daily averages climbing from $75/MWh on 16 August to a peak of $148/MWh on 19 August before easing back toward $105–$119/MWh into the weekend. Overall, it was a week defined by oversupply at the margins (frequent minor negative pricing overnight) sitting alongside genuine tightness at the peaks.
South Australia produced the week's most dramatic price action. SA1 posted a daily average as low as $11/MWh on 19 August — a day that included an extreme negative excursion to –$497/MWh — before rebounding to a $96/MWh average on 21 August and a $376/MWh peak spike that same day. Victoria and Tasmania both recorded major spikes on 19 August as well, with VIC1 touching $406/MWh and TAS1 reaching $374/MWh within the same volatile evening window around 23:05–23:10 UTC, a near-threefold jump from prior levels in each case. NSW1 and QLD1 were comparatively contained, with QLD1 averages sitting mostly in the $40–$74/MWh band across the week.
The WEM ran materially hotter than most NEM regions this week. WA1's daily average climbed from $75/MWh on 16 August to $145–$148/MWh through 18–19 August, with a peak interval spike to $381/MWh on 19 August — the sharpest print of the week in any region. Further spikes to $308.80/MWh (18 August, 14:50) and $261.13/MWh (22 August, 13:35) occurred against a generation backdrop of gas (CCGT/OCGT) combined with meaningful wind contribution, indicating the WEM continues to see tighter dispatch margins at peak periods than the NEM mainland.
Tasmania achieved 100% renewable generation (hydro, wind and rooftop solar) on at least four separate mornings this week — 18, 19, 20, 22 and 23 August — with hydro and wind combining for outputs regularly exceeding 1,200–2,600 MW. South Australia also posted several high-renewable intervals, including 97.9% on 18 August (wind-dominated at around 1,952 MW) and 93.1% on 23 August, with wind again the primary contributor.
These high-renewable periods were frequently associated with negative pricing rather than price stability — SA1, VIC1, TAS1, NSW1 and QLD1 all recorded multiple sustained negative-price intervals across the week, generally in the –$1 to –$20/MWh range, with SA1's overnight collapse to –$101/MWh on 19 August the most extreme instance. Curtailment risk during these overnight wind-heavy windows remains a live consideration for renewable asset operators bidding into low-demand periods.
Tasmania's T_BLINK_TV_NGZ constraint was the standout structural theme of the week, binding on at least five separate occasions (18, 20, 21 and 23 August) with an extraordinarily high shadow price of $8.352 million each time. This constraint consistently coincided with periods of strong hydro and wind output, pointing to a persistent transmission or network limitation within Tasmania rather than a simple generation-scarcity issue, and is worth monitoring for anyone with Tasmanian generation or load exposure.
Elsewhere, a severe NEM-wide constraint (F_T+LREG_0050) posted a shadow price of $232,000/MWh, and a further constraint (F_T+NIL_ML_RECL_L6) reached $2,944/MWh — both indicating episodes of significant dispatch inflexibility during the week. The VIC-NSW interconnector also ran at its export limit for periods, exporting over 718 MW from Victoria into NSW and acting as a key determinant of regional price convergence.
On FCAS, weekly average prices remained benign across all eight services — RAISEREG was the highest at $3.46/MWh, with LOWER6SEC at $0.46/MWh and the remaining regulation and contingency services all trading below $0.30/MWh on average. No material FCAS price spikes were evident this week despite the energy price volatility observed in TAS1 and SA1.
Gas hub prices held a tight, stable band across the week. STTM Sydney ranged from $10.86–$11.19/GJ, STTM Brisbane from $10.83–$11.41/GJ, and STTM Adelaide from $10.50–$11.10/GJ. DWGM Victoria was the softest of the group, trading between $9.75 and $10.10/GJ. There was no material directional trend — gas remained a steady input cost through the week's electricity price volatility.
LGC prices eased to $7.75 for the week ending 21 August, down from $8.50 the prior week, though still well above the $5.05–$5.85 range seen in mid-to-late July. The certificate market appears to have retraced modestly after a run-up through late July and early August, though remains elevated relative to its recent lows.
With Tasmania's persistent transmission constraint showing no signs of resolution and renewable output remaining strong across TAS1 and SA1, expect continued overnight negative-pricing episodes alongside sharp evening peak volatility in those regions. The WEM's tighter dispatch margins bear watching, particularly around early-afternoon and mid-afternoon periods where gas and wind interplay has driven spikes toward or above $300/MWh this week. Gas hub prices look set to remain range-bound barring any supply disruption, while LGC pricing will be one to watch for signs of whether the recent pullback continues or stabilises ahead of quarter-end compliance activity.
Get the weekly digest delivered to your inbox every Tuesday morning.
Subscribe