Negative prices (Storm Agnes)
Sun 24 Sep · Mon 25 Sep · Wed 27 Sep · Thu 28 Sep
Research notes
Figures are for London unless they say otherwise.
What happened
- Sun 24 Sep: London was below zero for 1 hour (longest spell half an hour from 14:30), min −0.2p at 14:30; average 11.3p, peak 35.0p at 18:00; all 14 regions at 0p or below; lowest −0.3p in Northern Scotland.
- Mon 25 Sep: London was below zero for 5 hours from 00:00, min −2.2p at 02:30; average 16.5p, peak 39.5p at 18:30; all 14 regions at 0p or below; lowest −2.6p in Northern Scotland.
- Wed 27 Sep: London was below zero for half an hour from 23:30, min −4.4p at 23:30; average 19.8p, peak 35.3p at 17:00; all 14 regions at 0p or below; lowest −5.2p in Northern Scotland.
- Thu 28 Sep: London was below zero for 4 hours (longest spell 2 hours from 03:30), min −6.9p at 05:00; average 16.0p, peak 38.1p at 18:30; all 14 regions at 0p or below; lowest −8.3p in Northern Scotland.
Likely causes
- Storm Agnes affected the UK on 27 and 28 Sep 2023, according to the Met Office's list of named storms for 2023/24. Source: Met Office, UK storm season 2023/24. (confirmed by source; its link to the prices is inference)
- Electric Insights: 25 Sep 2023 "saw the lowest ever wholesale power price recorded, at –£77.29/MWh". Source: Electric Insights, Power system records (Q3 2023). (confirmed by source; which market it means isn't stated)
- Sun 24 Sep, 14:30 (London's lowest half-hour): wind 19.3GW (58% of supply), solar 3.6GW, gas 3.3GW (10%), imports 1.2GW, total supply 33.2GW. Over the day wind averaged 16.7GW; the 2023 average was 9GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Mon 25 Sep, 02:30 (London's lowest half-hour): wind 16.5GW (62% of supply), solar 0GW, gas 3GW (11%), imports 0.5GW, total supply 26.4GW. Over the day wind averaged 12.9GW; the 2023 average was 9GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Wed 27 Sep, 23:30 (London's lowest half-hour): wind 18.1GW (62% of supply), solar 0GW, gas 3.8GW (13%), imports 1.1GW, total supply 29.5GW. Over the day wind averaged 11.4GW; the 2023 average was 9GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Thu 28 Sep, 05:00 (London's lowest half-hour): wind 17.1GW (63% of supply), solar 0GW, gas 3.2GW (12%), imports 0.6GW, total supply 27.3GW. Over the day wind averaged 15.3GW; the 2023 average was 9GW (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 Sun 24 Sep, Mon 25 Sep, Wed 27 Sep and Thu 28 Sep (19.3GW, 16.5GW, 18.1GW and 17.1GW, against 9GW for the year). (inference from NESO data)
- The low came overnight on Mon 25 Sep, Wed 27 Sep and Thu 28 Sep, when demand is at its lowest. (inference)
- Sun 24 Sep was at the weekend, when demand is lower. (inference)
- Elexon market index: Sun 24 Sep averaged £4.45/MWh with a low of −£58.14 at 23:30; Mon 25 Sep averaged £51.62/MWh with a low of −£77.29 at 04:00; Wed 27 Sep averaged £83.22/MWh with a low of −£31.34 at 00:00; Thu 28 Sep averaged £92.07/MWh with a low of −£0.22 at 05:00. Source: Elexon market index, Sun 24 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
High.
Gaps
- Trap: Modo Energy calls −£70/MWh on 2 Jul 2023 the record low for the EPEX hourly day-ahead market, and Electric Insights calls −£77.29/MWh on 25 Sep 2023 the lowest wholesale price recorded. They are probably different markets; don't call either "the" record without saying which.