Negative prices (midday, weekend)
Research notes
Figures are for London unless they say otherwise.
What happened
- Sat 14 Sep: London was below zero for 1 hour from 13:30, min −0.7p at 13:30; average 13.9p, peak 33.6p at 18:00; all 14 regions at 0p or below; lowest −0.8p in Northern Scotland.
Likely causes
- Sat 14 Sep, 13:30 (London's lowest half-hour): wind 12.6GW (38% of supply), solar 9.4GW, gas 3.1GW (9%), imports 1.7GW, total supply 33.2GW. Over the day wind averaged 9.7GW; the 2024 average was 9.4GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- The low came around midday on Sat 14 Sep, with solar at 9.4GW. (inference from NESO data)
- Sat 14 Sep was at the weekend, when demand is lower. (inference)
- Elexon market index: Sat 14 Sep averaged £34.99/MWh with a low of −£25.71 at 12:30. Source: Elexon market index, Sat 14 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.