Energy was last better‑than‑free: yesterday Next

Research notes

Figures are for London unless they say otherwise.

What happened

• Wed 21 Aug: London was below zero for 4.5 hours from 10:30, min −0.6p at 12:30; average 7.9p, peak 29.1p at 18:00; all 14 regions at 0p or below; lowest −0.7p in Northern Scotland.
• Thu 22 Aug: London was below zero for 9 hours (longest spell 4.5 hours from 11:00), min −2.1p at 03:30; average 7.1p, peak 33.4p at 18:30; all 14 regions at 0p or below; lowest −2.5p in Northern Scotland.
• Fri 23 Aug: London was below zero for 5 hours (longest spell 3 hours from 11:30), min −2.1p at 09:30; average 7.9p, peak 30.0p at 18:30; all 14 regions at 0p or below; lowest −2.5p in Northern Scotland.
• Sat 24 Aug: London was below zero for half an hour from 23:30, min −2.5p at 23:30; average 13.5p, peak 29.1p at 18:30; all 14 regions at 0p or below; lowest −3.0p in Northern Scotland.
• Sun 25 Aug: London was below zero for 11 hours (longest spell 7 hours from 07:00), min −2.7p at 15:00; average 5.2p, peak 28.4p at 18:30; all 14 regions at 0p or below; lowest −3.2p in Northern Scotland.

Likely causes

• Storm Lilian affected the UK on 22 and 23 Aug 2024, 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: "Wind power came its closest ever to meeting Britain’s entire demand for electricity early in the morning of 22 August." Source: Electric Insights, Power system records (Q3 2024). (confirmed by source)
• Mon 26 Aug 2024, the day after, was the summer bank holiday. Source: GOV.UK bank holidays. (confirmed by source)
• System warning published 25 Aug, 22:06: "A request for Emergency Assistance has been agreed on a GB connected Interconnector. The requesting party was NGESO. GB net flow will increase by 500 MW between 21:55 25/08/2024 to 23:30 25/08/2024." Source: Elexon system warnings. (confirmed by source)
• Wed 21 Aug, 12:30 (London's lowest half-hour): wind 14.8GW (43% of supply), solar 6.6GW, gas 1.9GW (6%), imports 4.1GW, total supply 34.8GW. Over the day wind averaged 15.2GW; the 2024 average was 9.4GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Thu 22 Aug, 03:30 (London's lowest half-hour): wind 18.4GW (62% of supply), solar 0GW, gas 4.1GW (14%), imports 0GW, total supply 29.4GW. Over the day wind averaged 15.5GW; the 2024 average was 9.4GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Fri 23 Aug, 09:30 (London's lowest half-hour): wind 15.3GW (45% of supply), solar 6.4GW, gas 2GW (6%), imports 3.5GW, total supply 34.1GW. Over the day wind averaged 12.2GW; the 2024 average was 9.4GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Sat 24 Aug, 23:30 (London's lowest half-hour): wind 14.8GW (57% of supply), solar 0GW, gas 2.6GW (10%), imports 0.9GW, total supply 26GW. Over the day wind averaged 9.8GW; the 2024 average was 9.4GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Sun 25 Aug, 15:00 (London's lowest half-hour): wind 14.9GW (51% of supply), solar 4.1GW, gas 2.3GW (8%), imports 1.3GW, total supply 29.4GW. Over the day wind averaged 14.3GW; 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 Thu 22 Aug (18.4GW, against 9.4GW for the year). (inference from NESO data)
• The low came around midday on Wed 21 Aug and Sun 25 Aug, with solar at 6.6GW and 4.1GW. (inference from NESO data)
• The low came overnight on Thu 22 Aug and Sat 24 Aug, when demand is at its lowest. (inference)
• Sat 24 Aug and Sun 25 Aug were at the weekend, when demand is lower. (inference)
• Elexon market index: Wed 21 Aug averaged £17.46/MWh with a low of −£16.87 at 12:30; Thu 22 Aug averaged £19.28/MWh with a low of −£19.09 at 03:30; Fri 23 Aug averaged £27.72/MWh with a low of −£12.61 at 04:30; Sat 24 Aug averaged £38.22/MWh with a low of −£1.74 at 15:30; Sun 25 Aug averaged £16.08/MWh with a low of −£22.86 at 13:00. Source: Elexon market index, Wed 21 Aug. (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

• None beyond what is said above.