GERT

Tail-risk intelligence

Grid notes 01 / About 90 seconds to read

Why can electricity use fall during a blackout?

A lower reading can mean less electricity was delivered—not that people needed less. That distinction changes what you can conclude about a grid.

GERT · Dresden Goehner · September 13, 2026 · Historical educational example

72 hourly ERCOT native-load observations, February 14–16, 2021, on a zero-to-80-GW scale. A dashed reference marks the reported onset of rotating outages at 01:25 CST on February 15. The curve falls but does not measure unmet demand or reliability.
Recorded load only. The vertical reference is an externally reported event time, not a measurement of lost load. Sources and all 72 values below. Open full-size graphic ↗
01 / Read the boundary

A measurement is not the whole system.

ERCOT reported that rotating outages began at 01:25 a.m. on February 15, 2021, after generating units became unavailable. When customers are disconnected, some intended electricity use cannot appear in the recorded load. Read the contemporaneous report.

What this curve cannot establish

  • Demand in the absence of interruptions.
  • The amount of electricity not supplied.
  • Whether reliability improved, or an intervention worked.

We do not attribute every change to outages. Weather, behavior, and other system conditions also matter.

Try a five-minute counterexample

Same meter. Two worlds.

Build two invented situations with identical electricity readings but different unmet demand. Change an assumption and inspect the arithmetic yourself.

Try the interactive explanation →
02 / Check your interpretation

Two questions. No sign-up.

Choose your answers, then reveal the explanation. Your first answers stay in the downloadable record. Nothing is sent to GERT.

1. The recorded load falls. What can this curve alone establish?
2. In a separate hypothetical one-hour example, load is 65,000 MW and assumed capacity is 60,000 MW. What is the arithmetic gap energy?
03 / Pass the question on

One link. One ready-to-use graphic.

For a class, a club message, or a reading list. Preserve the source credit and limitations when sharing.

Download PNGDownload SVG

Forwarding text and reuse notes

Original GERT material follows the repository MIT license; public raw data follows ERCOT's terms. Do not imply ERCOT or another organization endorses GERT. Download the complete forwarding pack and license notice.

Now change an assumption.

Open the winter case with an explicitly assumed 60,000 MW capacity and no load reduction. The arithmetic gap is a counterfactual exercise—not historical outage losses. Try other assumptions and export the calculation.

Explore the winter case →Leave a substantive review

Sources, exact values, and reuse

  1. ERCOT Native Load 2021 archive — the source of the 72 hourly observations. Interval starts, America/Chicago (CST here); MW in the data, GW on the chart.
  2. ERCOT news release, February 15, 2021 — the source of the rotating-outage start time. The release is contemporaneous, not a complete retrospective loss estimate.
  3. Exact plotted data and metadata · Figure generator · ERCOT data-use terms, section 5.

GERT is independent of ERCOT. No affiliation or endorsement is implied. The original graphic and explanation follow the repository MIT license; underlying data remains attributed to its source. Read the complete notice in the forwarding pack.

Inspect all 72 hourly source values
Hourly interval starts (CST), February 14–16, 2021
Interval startRecorded load (MW)
2021-02-14T00:00:00-06:0055282.612
2021-02-14T01:00:00-06:0054746.708
2021-02-14T02:00:00-06:0054701.390
2021-02-14T03:00:00-06:0055005.102
2021-02-14T04:00:00-06:0055630.169
2021-02-14T05:00:00-06:0056680.454
2021-02-14T06:00:00-06:0058071.474
2021-02-14T07:00:00-06:0059511.077
2021-02-14T08:00:00-06:0061299.993
2021-02-14T09:00:00-06:0063072.424
2021-02-14T10:00:00-06:0064185.234
2021-02-14T11:00:00-06:0064864.156
2021-02-14T12:00:00-06:0065047.452
2021-02-14T13:00:00-06:0065028.901
2021-02-14T14:00:00-06:0065188.549
2021-02-14T15:00:00-06:0065556.735
2021-02-14T16:00:00-06:0066468.018
2021-02-14T17:00:00-06:0068094.825
2021-02-14T18:00:00-06:0069635.087
2021-02-14T19:00:00-06:0069692.485
2021-02-14T20:00:00-06:0069324.247
2021-02-14T21:00:00-06:0068473.934
2021-02-14T22:00:00-06:0067200.980
2021-02-14T23:00:00-06:0066270.516
2021-02-15T00:00:00-06:0065777.077
2021-02-15T01:00:00-06:0063910.401
2021-02-15T02:00:00-06:0053982.966
2021-02-15T03:00:00-06:0054102.714
2021-02-15T04:00:00-06:0054522.956
2021-02-15T05:00:00-06:0051839.580
2021-02-15T06:00:00-06:0051147.726
2021-02-15T07:00:00-06:0051220.191
2021-02-15T08:00:00-06:0049646.299
2021-02-15T09:00:00-06:0049443.179
2021-02-15T10:00:00-06:0048615.527
2021-02-15T11:00:00-06:0047548.021
2021-02-15T12:00:00-06:0046197.976
2021-02-15T13:00:00-06:0045423.548
2021-02-15T14:00:00-06:0045100.613
2021-02-15T15:00:00-06:0045416.829
2021-02-15T16:00:00-06:0045767.296
2021-02-15T17:00:00-06:0045425.706
2021-02-15T18:00:00-06:0045061.707
2021-02-15T19:00:00-06:0044257.287
2021-02-15T20:00:00-06:0044364.439
2021-02-15T21:00:00-06:0044894.441
2021-02-15T22:00:00-06:0044100.045
2021-02-15T23:00:00-06:0043704.295
2021-02-16T00:00:00-06:0044070.049
2021-02-16T01:00:00-06:0044524.149
2021-02-16T02:00:00-06:0045258.654
2021-02-16T03:00:00-06:0046108.298
2021-02-16T04:00:00-06:0045598.004
2021-02-16T05:00:00-06:0045681.929
2021-02-16T06:00:00-06:0046501.875
2021-02-16T07:00:00-06:0046796.658
2021-02-16T08:00:00-06:0045855.511
2021-02-16T09:00:00-06:0044947.878
2021-02-16T10:00:00-06:0044196.114
2021-02-16T11:00:00-06:0044291.851
2021-02-16T12:00:00-06:0044273.062
2021-02-16T13:00:00-06:0043977.836
2021-02-16T14:00:00-06:0045176.698
2021-02-16T15:00:00-06:0045569.701
2021-02-16T16:00:00-06:0046123.615
2021-02-16T17:00:00-06:0046562.497
2021-02-16T18:00:00-06:0045843.067
2021-02-16T19:00:00-06:0045498.773
2021-02-16T20:00:00-06:0045306.602
2021-02-16T21:00:00-06:0044392.860
2021-02-16T22:00:00-06:0043538.402
2021-02-16T23:00:00-06:0042691.437