Negative prices (weekend)
Sat 23 Mar · Sun 24 Mar
Research notes
Figures are for London unless they say otherwise.
What happened
- Sat 23 Mar: London was below zero for 1 hour (longest spell half an hour from 08:00), min −0.6p at 08:00; average 4.5p, peak 26.3p at 17:30; all 14 regions at 0p or below; lowest −0.8p in Northern Scotland.
- Sun 24 Mar: London was below zero for 1.5 hours from 08:00, min −3.8p at 08:00; average 9.9p, peak 32.5p at 18:30; all 14 regions at 0p or below; lowest −4.5p in Northern Scotland.
Likely causes
- Sat 23 Mar, 08:00 (London's lowest half-hour): wind 19.8GW (58% of supply), solar 4GW, gas 2.2GW (7%), imports 2.7GW, total supply 34.2GW. Over the day wind averaged 18.8GW; the 2024 average was 9.4GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Sun 24 Mar, 08:00 (London's lowest half-hour): wind 17.4GW (54% of supply), solar 4GW, gas 2.8GW (9%), imports 2.1GW, total supply 32.1GW. Over the day wind averaged 11.2GW; the 2024 average was 9.4GW (29%). 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 Sat 23 Mar and Sun 24 Mar (19.8GW and 17.4GW, against 9.4GW for the year). (inference from NESO data)
- Sat 23 Mar and Sun 24 Mar were at the weekend, when demand is lower. (inference)
- Elexon market index: Sat 23 Mar averaged £13.23/MWh with a low of −£16.27 at 09:00; Sun 24 Mar averaged £41.40/MWh with a low of −£14.16 at 08:00. Source: Elexon market index, Sat 23 Mar. (confirmed by source; a short-term index, not the day-ahead auction Agile follows)
Wider context that week
- Electric Insights: the highest ever share of electricity from clean sources, over 95%, came on 23 Mar 2024. Source: Electric Insights, Power system records (Q1 2024). (confirmed by source)
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.