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How Texas’s grid emergency unfolded during the February 2021 freeze
ERCOT began rotating outages on 15 February 2021 and ordered cuts that peaked at 20,000 megawatts that evening. The grid operator cancelled its final controlled outage orders early on 18 February and returned to normal operation the next day.
Sources checked
- 8 February 2021Start of the federal study window
The federal inquiry began its event window on 8 February and covered Texas and the South Central United States. · Regional event window Source 1
- 14 February 2021ERCOT issued a winter weather watch
The grid operator issued a watch for freezing precipitation and also flagged pressure on available reserves. · ERCOT Source 1
- 15 February 2021, 1:25 a.m.Rotating outages began
ERCOT’s first public notice said it began rotating outages at 1:25 a.m. after entering emergency conditions. · ERCOT Source 2
- 15 February 2021, 2 a.m.Ordered cuts reached 10,500 MW
The federal report put cumulative load shed orders at 10,500 MW at this point in the morning. · ERCOT Source 1
- 15 February 2021, 7 a.m.Federal averaging window began
Investigators measured an average of 34,000 MW of unavailable expected generation from this point to 1 p.m. on 17 February. · ERCOT Source 1
- 15 February 2021, 7 p.m.Ordered cuts reached their peak
The federal inquiry put ERCOT’s peak manual load shed at 20,000 MW. · ERCOT Source 1
Show 6 more dates
- 17 February 2021, 1 p.m.Federal averaging window ended
The average covered 54 hours and included generation already unavailable when the cold-weather event began. · ERCOT Source 1
- 17 February 2021, afternoonGrid operator announced staged restoration
ERCOT reported enough generation to begin restoring 1,000 MW of demand per hour that afternoon. · ERCOT Source 3
- 18 February 2021, 12:42 a.m.Last firm load shed orders cancelled
ERCOT cancelled its remaining controlled outage orders. Local operators still had restoration work. · ERCOT Source 4
- 19 February 2021, 7:30 a.m.Forced outages remained
ERCOT’s update put generation on forced outage at roughly 34,000 MW despite an improved balance between supply and demand. · ERCOT Source 5
- 19 February 2021, 10:35 a.m.Grid returned to normal operations
ERCOT’s legislative briefing recorded its exit from emergency operation at 10:35 a.m. · ERCOT Source 4
- 20 February 2021Federal study window ended
The inquiry recorded 4,124 generation outages, output reductions or failures to start across the event area over the full window. · Regional event window Source 1
Choose an event to jump to its source and see whether it refers to ERCOT or the regional inquiry.
Two different figures describe the supply gap
The 20,000 MW figure is the peak amount of demand ERCOT ordered disconnected to balance the system. The federal report’s 34,000 MW figure is an average of unavailable expected generating capacity over 54 hours. The measures describe different sides of the grid balance. Source 1
One generating unit could appear more than once
The inquiry counted 4,124 incidents involving 1,045 individual generating units across Texas and the South Central United States. Its incident count includes units that went offline, units that reduced output and units that could not start. A unit could have several incidents. Source 1
What investigators attributed to freezing and fuel
The federal staff assigned 44.2% of the regional generation incidents to freezing and 31.4% to fuel issues. These are shares of incidents in the inquiry. The underlying generators had different capacities, so a share of incidents describes a different quantity from a share of megawatts unavailable. Source 1
Recovery had separate grid and local milestones
ERCOT cancelled its last firm load shed orders on 18 February. Some outages caused by ice damage still needed local repair. Its morning update on 19 February reported continued forced outages at generators even as ERCOT prepared to leave emergency operations. Source 4 Source 5