Solar holds midday down; the 8 PM-9 PM net-load ramp is the test

Today's decision window is the 8 PM-10 PM CDT net-load ramp, where the cleared day-ahead curve and MetisCast diverge by up to $94.5/MWh at 9 PM CDT; the gap closes only if real-time nears the cleared peaks while load tracks the 91,603 MW forecast. Since the prior issue, the forecast gross-load peak rose 631 MW to 91,603 MW, the day-ahead curve cleared evening peaks of $141.2/MWh (ERCOT Hub Average) and $162.9/MWh (North Hub) at 8 PM CDT, and West Hub's cleared curve reached $157.8/MWh.

Watch the 8 PM-9 PM CDT real-time prints against those peaks, realized load against 91,603 MW, and whether MetisCast's $67.0/MWh P50 narrows the gap.

Real-time prices settled beneath their own day-ahead awards across every hub over the trailing 24 hours, mostly on a single $-7.6/MWh systemwide convergence component, itself near the 4th percentile of its trailing 90-day range. After removing that common piece, North Hub's $-8.1/MWh raw spread leaves a $-0.5/MWh residual, South Hub's $-5.0/MWh leaves $2.6/MWh, West Hub's $-8.3/MWh leaves $-0.7/MWh, and Houston Hub's $-8.9/MWh leaves $-1.3/MWh, with the common component covering 85% of that raw figure. None crosses its own historical residual threshold (North $5.4/MWh, South $6.0/MWh, West $6.7/MWh, Houston $6.1/MWh): the discount is systemwide, not one hub separating from the rest.

Today's cleared day-ahead curve prices a sharper evening climb than yesterday's: ERCOT Hub Average clears to $141.2/MWh at Aug 20, 8 PM CDT versus $91.5/MWh a day earlier; North Hub to $162.9/MWh versus $103.5/MWh; South Hub to $111.2/MWh versus $75.0/MWh; Houston Hub to $132.8/MWh versus $88.2/MWh. All four now peak at the same Aug 20, 8 PM CDT hour, tighter than yesterday's Aug 19, 6 PM to 9 PM CDT peak spread.

MetisCast's same-vintage P50, issued Aug 20, 7:45 AM CDT, does not back that size: it peaks at $67.0/MWh at Aug 20, 7 PM CDT, an hour ahead of the cleared curve's high, averaging $22.5/MWh under it across 17 joined hours and widening to a $94.5/MWh gap at Aug 20, 9 PM CDT. Its own P10-P90 band is widest, $143.9/MWh, at Aug 20, 7 PM CDT, so the model itself is not pricing confidence into that window.

Watch the Aug 20, 8 PM to 9 PM CDT real-time prints against these cleared peaks: settling near them confirms the ramp's priced size, while settling closer to MetisCast's path, or a cross-location median RT-DA spread breaking below its recent error band, says the premium is overstated and reframes today's convergence read before the next issue.

MetisCast prices ERCOT Hub Average -$22.5/MWh against the cleared day-ahead curve across 17 joined hours. Its P50 tops out at $67/MWh at Aug 20, 7 PM CDT while the market cleared $141.2/MWh at Aug 20, 8 PM CDT. The two agree on when the evening matters and disagree on what it pays.

North Hub's real-time price averaged $28.0/MWh over the trailing 24 hours, above South Hub's $24.6/MWh, and that split holds into the cleared evening curve: North's day-ahead award reaches $162.9/MWh versus South's $111.2/MWh, both at the Aug 20, 8 PM CDT hour. West Hub's real-time mean of $26.2/MWh and day-ahead high of $157.8/MWh sit closer to North than South, putting West on the north side of tonight's ramp rather than the south.

All four hubs carry a similar real-time discount to their own day-ahead award (North $8.1/MWh, West $8.3/MWh, Houston $8.9/MWh) against a $7.6/MWh systemwide average; South's is smaller at $5.0/MWh. The common component explains 85% of Houston's raw gap, leaving a $1.3/MWh local residual, so this reads as shared systemwide convergence, not a Houston-specific move.

Wind's path averages 12,885 MW while solar peaks at 33,956 MW at Aug 20, 1 PM CDT. The pre-storage net-load path peaks at 70,981 MW at Aug 20, 9 PM CDT on an 11,908 MW/h ramp into 8 PM CDT, both at the 94th percentile of their trailing 90-day distributions, exceptional versus recent history.

Resource outage capacity in effect is 7,527 MW, the 5th percentile of the same local hour and weekday type over the trailing 90 days, unusually low. Capacity less load and the ancillary-service requirement reads -377.6 MW, the 24th percentile of the trailing 90-day range, soft but inside the recent band. This is a supply-side tailwind into the ramp, not a scarcity signal.

MetisCast's Aug 20, 7:45 AM CDT vintage widens to a $143.9/MWh P10-P90 band at Aug 20, 7 PM CDT, the hour its P50 path tops at $67.0/MWh, an hour ahead of and well under the $141.2/MWh cleared day-ahead peak at 8 PM CDT. The model's own uncertainty says the evening is not resolved with confidence.

ERCOT's OCN for extreme heat runs Aug 20 through Aug 25 across the North Central and South Central regions, context for the load path, not an independent price driver. Grid event: OCN

Today's desk signal is the cross-location RT-DA spread, not any single hub. Houston Hub's real-time discount to its day-ahead award averaged $-8.9/MWh over 24 joined hours, but $-7.6/MWh of that is the systemwide RT-DA component, leaving a $-1.3/MWh Houston residual inside its own band. North (-$0.51/MWh) and West (-$0.72/MWh) residuals sit the same way; South's runs $2.56/MWh positive. All four stay inside their own thresholds, so none is separating from the system.

Watch the Aug 20, 8 PM-10 PM CDT window for two triggers: the cross-location median RT-DA spread clearing above $8.4/MWh or below -$9.7/MWh, or any hub's residual breaking its own threshold (Houston $6.1/MWh, North $5.4/MWh, West $6.7/MWh, South $6/MWh) while the median stays inside that band. Open the Hub detail real-time versus day-ahead charts and the hub comparison chart to track both live.

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. This issue could not close 3 analytical gaps: residual dispatchable demand, reserve, prc and contingency coverage, weather-to-market translation. Each is stated in the analysis rather than filled in by inference.

Source and quality note. 29 of 29 requested issue series were available; 16 longer-lookback series supported deterministic context. 11 event records were known at cutoff and 2 unchanged records were suppressed. Knowledge cutoff: Aug 20, 8:00 AM CDT.