Midcontinent Independent System Operator's real-time market hit the $10,000 per megawatt-hour cap as late-summer heat, a sharp solar drop, and weaker imports squeezed available power, Enverus said in a Thursday note.
During the 6-8 p.m. ET period on Sept. 2, demand ran 4,300 MW to 5,700 MW above day-ahead forecasts as hotter temperatures pushed load higher than expected.
Solar generation plunged from about 18,350 MW at midday to 137 MW by 8 p.m. ET, removing nearly 18 GW of supply as system demand neared its evening peak.
Lower imports and transfer limits compounded the shortfall, moving MISO from an energy emergency alert level one at 6:48 p.m. ET to level two by 7:11 p.m. ET.
Battery resources supplied power during the event but depleted their available energy before the tightest conditions arrived, leaving less flexibility when prices surged, Enverus said.
At the Indiana Hub, real-time prices averaged $1,630.70/MWh from 6-7 p.m. ET and $4,118.32/MWh from 7-8 p.m. ET, versus day-ahead averages of $347/MWh and $257/MWh.
Enverus could not confirm a possible generation decline near Fermi and other units, so it identified roughly 5 GW of load forecast error, solar losses, and weaker imports as confirmed drivers.
The episode showed that imports may not provide a dependable hedge when neighboring systems face tight conditions or transfer limits during MISO's evening ramp.
The event also suggests forward power curves and real-time volatility may need higher cap-risk pricing, as routine supply and demand shifts can trigger extreme prices, Enverus said.