MetisCast undercuts cleared day-ahead by $6.8/MWh across tonight's curve

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Prior call. A publication gap left the preceding issue ungraded. This issue's observation window opens Aug 24, 8 AM CDT, after that horizon closed; the intervening day was not published. This issue advances a new thesis without a graded predecessor.

Since yesterday's issue, North Hub's real-time-versus-day-ahead relationship reversed hard. Its local residual, the piece left after removing the systemwide convergence component, widened by $12.1/MWh to $8.2/MWh, while Houston Hub's eased by $7.3/MWh to -$6.0/MWh and South Hub's eased by $10.0/MWh to -$5.8/MWh. All three now sit outside their own calibrated residual bands, and North's move is the sharpest of the three. North's raw spread averaged $10.8/MWh across the 24 joined hours, but the common systemwide component, the same $2.5/MWh convergence result running through every hub, accounts for only a small share of that. The $8.2/MWh residual is the location-specific piece that broke North's band.

North Hub's real-time price also printed the day's clear high, $132.20/MWh at hour-ending 7 PM CDT on Aug 24, well above the ERCOT Hub Average's $101.20/MWh high the same hour; South Hub topped out lower at $75.70/MWh and Houston at $89.00/MWh. That gap between North and the rest of the footprint, not the ERCOT Hub Average level, is the relationship worth tracking into tonight's settlement.

It sits alongside today's already-flagged negative evening capacity margin; the margin figure lives elsewhere in this issue, but the RT-DA split is what tests it hour by hour. No outage or notice record in this issue explains why North's residual widened while South's and Houston's moved the other way; ERCOT's extreme-heat operating notice running through today frames the window without pointing to the split's cause. Public Notices

The call holds if the cross-location median RT-DA spread stays inside its calibrated band and realized load tracks within its forecast tolerance through the peak; it breaks if that median spread turns more negative than the band's floor, or load falls short of the forecast by more than the tolerance before the peak. Watch North Hub's residual first, it is the location farthest outside its own history.

MetisCast prices ERCOT Hub Average -$6.8/MWh against the cleared day-ahead curve across 17 joined hours. Its P50 tops out at $71/MWh at Aug 25, 7 PM CDT while the market cleared $99.1/MWh at Aug 25, 8 PM CDT. The two agree on when the evening matters and disagree on what it pays.

At Aug 24, 7 PM CDT, North Hub's real-time price hit $132.20/MWh, the highest of the five tracked points and $31.00/MWh above the ERCOT Hub Average's $101.20/MWh high. West Hub followed at $107.80/MWh; Houston Hub topped out at $89.00/MWh and South Hub at $75.70/MWh. North and west carried that hour's premium while south and the coast stayed comparatively contained.

Today's cleared day-ahead awards extend that same shape. North Hub's award peaks at $110.40/MWh and West Hub's at $108.00/MWh, both at 8 PM CDT; Houston's award tops out lower at $96.00/MWh, also 8 PM CDT; South Hub's award peaks lowest at $84.50/MWh, one hour later at 9 PM CDT. The day-ahead market has already priced a geographic premium into North and West for tonight, with South a step behind.

The extreme-heat OCN active through Aug 25 describes today's operating backdrop, not why the premium concentrates north and west. Watch whether South's later, lower peak holds against the North/West lead as the evening settles. Public Notices

Today's gross-load forecast peaks at 90,544 MW at 5 PM CDT, high versus its trailing 90-day range, with net load then accelerating into the evening hours the capacity margin already marks as the day's tightest window. Resource outage capacity in effect stands at 9,012 MW, inside the central range of its same local-hour history over the trailing 90 days, so today's outage picture is not unusual. Reliability Unit Commitment volume rose through Aug 24's evening hours, concentrated in Houston and South, easing back overnight. Grid event: 3,058 MW of RUC-committed capacity

MetisCast, Ask the Grid's probabilistic price model, peaks its P50 path at $71.04/MWh at 7 PM CDT, an hour ahead of the cleared day-ahead curve's $99.12/MWh peak at 8 PM CDT. Averaged across the 17 joined hours, MetisCast prices $6.8/MWh below the cleared curve on a signed basis, with the largest single-hour gap, $58.7/MWh, at 9 PM CDT. Its widest P10-P90 band across the frozen horizon, $134.62/MWh, lands at that same 7 PM CDT hour, so the below-curve lean carries its least confidence right at the call. That combination leaves tonight's cleared premium unconfirmed by the model rather than validated by it. Whether the gap and the band close together or widen through the ramp is the signal to track, not the model's stance alone. An active extreme-heat operating condition notice covers the period through Aug 25, consistent with today's load peak but not tied to the model-market gap in the sources available.

Industry pushback on ERCOT's interconnection study process surfaced this week, a forward risk for future capacity additions, not tonight's balance. Industry warns of blackouts, economic woes if Texas overreacts to data center, transmission line anger | State | dentonrc.com

Desks across the four hubs should treat today's decision window as the checkpoint for tonight's basis, not the raw hub level. The controlling trigger is the cross-location median RT-DA spread against its calibrated band: above the upper edge, check reserves and renewable performance; below the lower edge, the evening premium is overstated across locations. Realized system load against the cutoff vintage is a second, independent input, not a price verdict on its own.

Houston and South Hub's residuals eased this issue while the evening RUC-commitment peak, concentrated in Houston and South, sits on the outage-and-congestion view, not the basis desk. Open the hub detail real-time-versus-day-ahead charts and the load-and-capacity view ahead of the evening settlement. The regional-overlay case triggers only if one hub's own residual breaks its threshold while the system-wide spread stays inside band. Grid event: 3,058 MW of RUC-committed capacity

Forecast-vintage policy. Every input in this issue was published at or before the knowledge cutoff. Forecast series are the latest vintage available at that instant and are never revised after the fact; realized history used for percentiles is guarded by the same cutoff. The preceding issue's frozen vintage is stored with the issue, so a revision is measured against what was actually published, not against a later correction. Not covered by this issue's data: Residual dispatchable demand; Reserve, PRC and contingency coverage; Weather-to-market translation. Each limitation is stated where it applies rather than filled in by inference.

Source and quality note. 29 of 29 requested issue series were available; 16 longer-lookback series provided the historical baselines. 36 event records were known at cutoff and 2 unchanged records were suppressed. Knowledge cutoff: Aug 25, 8:00 AM CDT.