Five minutes with wind_mw in grid-energy-load

Someone asked what is in wind_mw on grid-energy-load, and the honest answer took one query.

8,760 rows, no nulls, 6,314 distinct values. Wind generation.

The five-number version: min 45, p10 254, median 589, p90 1,382, max 4,200. The mean is 729.

The p10 to p90 band — 254 to 1,382 — is where ordinary rows live, and it is the pair worth quoting when somebody asks what to expect. Min and max describe the two strangest rows in the table and nothing else; they are useful for spotting impossible values and misleading for everything else.

select
  count(*)                  as rows,
  count(wind_mw)            as present,
  count(*) - count(wind_mw) as nulls,
  count(distinct wind_mw)   as distinct_values
from grid_energy_load;

The mean sits 24% above the median, which is the whole story: anything that reports the average of wind_mw is reporting a number most rows are below. Put the median next to it or drop the mean.

Where this bites: a filter like wind_mw > 729 reads as "above average" and selects a minority of rows — a smaller minority than the phrase suggests to whoever asked for it. If the request was "the typical ones", the threshold they meant was 589.

The grain is one row per hour, which is the context every one of those numbers depends on. None of them survive a change of grain, which is why "profile the column" and "profile the table" are the same job. Full schema, and the CSV, on the dataset page.