Price spike (at the cap)
Research notes
Figures are for London unless they say otherwise.
What happened
- Mon 24 Sep: London peaked at 35.0p at 18:30 (Agile's 35p cap), average 17.0p, lowest 12.0p at 00:30; highest anywhere 35.0p in Eastern England.
Likely causes
- Mon 24 Sep, 18:30 (London's peak): wind 2.2GW (6% of supply), solar 0GW, gas 15.9GW (41%), imports 3.1GW, total supply 38.9GW. Over the day wind averaged 4.2GW; the 2018 average was 5.8GW (17%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Wind was less than half its yearly average at the peak on Mon 24 Sep (2.2GW, against 5.8GW for the year), so gas made up the gap. (inference from NESO data)
- The peak came in the early evening on Mon 24 Sep, when demand is highest and there is no solar. (inference)
- Elexon market index: Mon 24 Sep averaged £72.65/MWh with a high of £107.82 at 19:30. Source: Elexon market index, Mon 24 Sep. (confirmed by source; a short-term index, not the day-ahead auction Agile follows)
Wider context that week
- Storm Bronagh (Thu 20 Sep to Fri 21 Sep) was within a few days of it. Source: Met Office, UK storm season 2018/19. (confirmed by source; its effect on these prices is inference)
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.