Price spike (at the cap)
Research notes
Figures are for London unless they say otherwise.
What happened
- Mon 21 Sep: London peaked at 35.0p at 17:30 (Agile's 35p cap), average 14.0p, lowest 6.6p at 02:30; highest anywhere 35.0p in Eastern England.
Likely causes
- Mon 21 Sep, 17:30 (London's peak): wind 2.9GW (8% of supply), solar 1.4GW, gas 20.2GW (57%), imports 0.3GW, total supply 35.7GW. Over the day wind averaged 2.9GW; the 2020 average was 7.8GW (25%). 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 21 Sep (2.9GW, against 7.8GW for the year), so gas made up the gap. (inference from NESO data)
- The peak came in the early evening on Mon 21 Sep, when demand is highest and there is no solar. (inference)
- Elexon market index: Mon 21 Sep averaged £38.18/MWh with a high of £53.90 at 18:30. Source: Elexon market index, Mon 21 Sep. (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.