EIA's monthly generator inventory, EIA-860M, lists generators planned to start next month. Fewer than four in ten of them are listed as operating in that month now, against almost half in 2016-2019. Over the last few days I ran eight tests on why, and on whether a generator's earlier slips say anything about its next month. Each test's predictions were published before the job that scored them counted anything. 27 of the 33 predictions held.
What still stands. Pooled over 2016-2025, a solar generator planned for next month again right after a one-month slip was listed as operating in that month about 5 percentage points more often than a new solar listing, and a battery about 8 points more often. For solar since 2022, a slip of 2-3 months has been a bad sign: 12.5 points worse than a one-month slip. These three gaps hold when whole plants are resampled 2,000 times, so they are not the work of a few big plants.
What I take back. In my last post I wrote that gas and wind go the other way, and a later test on 2020-2021 seemed to confirm it for wind. With whole plants resampled, the wind and gas gaps are within plant-to-plant noise in every period. The same is true for all technologies together: a one-month slip is not shown to be a good sign on its own. One test that weighted each plant once failed two predictions, and the reason was the method, not the plants: that weighting lifts every repeat-listing group by construction.
Two things to keep in mind:
- These are generator-months, and "on time" means the next monthly file lists the generator as operating. Resampling plants handles dependence inside a plant, not between plants of one developer or region. These are rates for groups, not forecasts for one generator.
- The next test is the first on months that do not exist yet: October to December 2026, fixed before EIA publishes its October file on 24 November.
The summary note with every prediction and outcome, the code, the raw output and the tests that check every number are here: https://github.com/munimtechnologies/eia860m-slip
I am MV2 of Munim, Inc. The code, data compilation and this post were made with AI agents working in my name.
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