California (CAISO) — no forecast-error regime change detected
The day-ahead forecast's error has stayed within its calibrated band. Not a certificate that nothing happened.
quiet streak 5.5 yearsbudget ≈1 false page per BA-yearwatching since Jan 2021
5.68%
mean abs. forecast error
of demand (MAPE)
25,283 MW
mean demand
902 MW
typical error
median |error|
7,931 MW
worst-hour error
99th pctile |error|
The evidence, last two weeks
Because the baseline is the operator’s own forecast, seasonality is subtracted for free — what’s left is the miss. The detector pages only when that miss enters a new regime and clears the page line.
Real EIA-930 data for California (CAISO) — the last 336 hourly points. The forecast is the grid operator’s own day-ahead demand forecast (not ours); the error is actual − forecast, peaking at +10,665 MW in this window. The evidence statistic stayed under the page line: no regime change detected. That is not proof nothing happened. Back-in-band is a display heuristic, not a certificate of absence.
Forecast-error regime changes0 in the monitored history
Each is a dated page inside the stated budget. Labels attach only where a window overlaps a documented grid-stress event — never invented. We detect that the forecast’s error changed regime, not that the grid failed or why.
No forecast-error regime change has cleared this grid’s page budget in the monitored history. Absence of entries is not proof nothing happened — it means nothing crossed the page line.
How this verdict is formed
The hourly error runs through a conformal band that learns California (CAISO)’s own normal forecast-error rate, into a Shiryaev–Roberts e-detector on a bounded rolling window. An alarm fires only when accumulated evidence crosses the page line — and because the statistic is anytime-valid, checking as often as you like never inflates the false-alarm rate. Full recipe, and exactly what we do not claim, on the methodology page.
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A live status pill for California (CAISO), refreshed every publish. Drop it in a README, status page, or dashboard — it always shows the current verdict and links back here. It reads no regime change while the forecast holds, and flips to forecast drift detected when the e-detector pages.
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