CALC-134

The week with the lowest wind and solar share among those starting November to February since 2022, and the 2024 shares for contrast

REGISTERED 2026-10-13. Drafted for QST-021, checked by a second reader (FIX, all applied before landing), landed by SBSP-coord. The commit that landed it names the draft and the check. Script: qst021-still-week.py. verified: -.

Feeds the opening of the QST-021 article and the still-week interactive. Answers QST-021. Basis: per cent of the dataset's GENERATION total (which includes imports), summed over half-hours; Great Britain; timestamps as printed in the file.

Script. qst021-still-week.py, run with python -I on the filed CSV.

Why it was needed. The article opens on a real, dated still week. The dataset gives half-hourly output by source; the stillest week has to be found and its shares computed.

Inputs.

Working, transcribed (script output).

complete 7-day windows ranked: 540 2024-11-03 to 2024-11-09 wind 10.0% solar 0.7% gas 51.8% nuclear 14.3% imports 12.0% biomass 8.0% 2022-12-09 to 2022-12-15 wind 12.0% solar 1.2% gas 54.2% nuclear 14.3% imports 7.0% biomass 5.1% 2023-11-26 to 2023-12-02 wind 13.2% solar 1.6% gas 52.1% nuclear 11.8% imports 8.8% biomass 7.0% 2025-01-16 to 2025-01-22 wind 14.2% solar 1.0% gas 56.2% nuclear 9.4% imports 7.2% biomass 7.6% 2023-02-27 to 2023-03-05 wind 13.5% solar 2.3% gas 54.4% nuclear 11.6% imports 10.5% biomass 5.1% calendar 2024 wind 29.4% solar 5.0% gas 25.8% nuclear 13.7% imports 15.7% biomass 6.7%

Result: from 3 to 9 November 2024, wind made 10.0 per cent of the total, solar 0.7 per cent and gas 51.8 per cent; over calendar 2024, wind made 29.4 per cent, solar 5.0 and gas 25.8.

Where this fails. - Data revisions. NESO says the data are subject to change by a cleansing process; a later download may give slightly different shares. The figures are for the file filed on 2026-10-13. - Definitions. NESO's field list defines GENERATION as the "Sum of gas, coal, nuclear, wind, wind embedded, hydro, imports, biomass, others, solar and storage." The shares are therefore of supply including imports, not of British generation alone. NESO's dataset page says batteries (net discharge) and transmission-connected solar farms are counted under OTHER, pumped storage is the STORAGE column, net-negative values are cut to zero, and updates to show battery and transmission solar values will follow later in 2026. So SOLAR leaves out transmission-connected solar, STORAGE is pumped-storage discharge only, and a later download will differ in OTHER, SOLAR and STORAGE. The page also says seasonal decomposition has been applied to correct missing or irregular data points, so some values are modelled, not metered. NESO's field list gives WIND_EMB no description; it is taken here as embedded (distribution-connected) wind, and how NESO derives it was not checked. - Choices. "Stillest" here means the lowest share of the total from wind plus solar, over 7 calendar days starting between November and February from 1 January 2022 to 28 February 2026. A different length, month range or start year could pick a different week. 16 to 22 December 2021 had a lower share (wind 7.5, solar 0.5, together 8.0 per cent; mean wind 2,728 MW against 3,287 MW for the chosen week), so "lowest" holds from 2022 only. Ranked from 2009, the lowest would be a week starting 16 February 2010 (0.2 per cent). The chosen week also ranks first on wind share alone, on transmission-connected wind alone and on mean wind output, so the ranking key does not change the answer. - Weighting. Shares are the sum of megawatts over the sum of GENERATION across the period, not the average of the file's half-hourly percentage columns. For calendar 2024 the average of the percentage columns gives solar 4.7 and gas 25.0 per cent where this record gives 5.0 and 25.8. - The wind did not stop. In the chosen week mean wind output (WIND plus WIND_EMB) was 3,287 MW, 35 per cent of the 2024 mean of 9,410 MW, and the lowest half-hour was 1,013 MW. The week has the lowest share of supply from wind and solar, not no wind. - Timestamps are used as printed. The rows carry no zone, but NESO's field description for DATETIME says "given in UTC" (read from the dataset's API metadata, datastore_search, 2026-10-13). All 311,745 timestamps are exactly 30 minutes apart with none missing or repeated, including on clock-change days, so they are not local time. Every ranked window lies between 1 November and 6 March and the 2024 year ends fall in GMT, so UTC equals British time for every figure here.

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