Negative prices (overnight)
Research notes
Figures are for London unless they say otherwise.
What happened
- Wed 20 Oct: London was below zero for half an hour from 00:30, min −2.1p at 00:30; average 27.1p, peak 35.0p at 06:00; all 14 regions at 0p or below; lowest −2.5p in Northern Scotland.
Likely causes
- Wed 20 Oct, 00:30 (London's lowest half-hour): wind 14.9GW (57% of supply), solar 0GW, gas 3.1GW (12%), imports 1.1GW, total supply 26GW. Over the day wind averaged 12.1GW; the 2021 average was 7.1GW (22%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Wind was well above its yearly average at the lowest half-hour on Wed 20 Oct (14.9GW, against 7.1GW for the year). (inference from NESO data)
- The low came overnight on Wed 20 Oct, when demand is at its lowest. (inference)
- Elexon market index: Wed 20 Oct averaged £159.54/MWh with a low of −£1.64 at 02:30. Source: Elexon market index, Wed 20 Oct. (confirmed by source; a short-term index, not the day-ahead auction Agile follows)
Wider context that week
- Nothing notable found for that week.
Confidence
Medium. The grid figures fit the prices, but no report found names a cause for this date.
Gaps
- No news report or official write-up found that ties this date to a cause; the causes above are from the data.
- Elexon's system warnings feed has no entries before mid-2023, so warnings for these days couldn't be checked there.