Energy was last better‑than‑free: yesterday Next

Research notes

Figures are for London unless they say otherwise.

What happened

• Tue 29 Dec: London peaked at 34.1p at 16:30, average 14.4p, lowest 10.1p at 04:30; highest anywhere 35.0p in Eastern England.
• Wed 30 Dec: London peaked at 35.0p at 16:30 (Agile's 35p cap), average 15.2p, lowest 10.1p at 03:30; highest anywhere 35.0p in Eastern England.
• Thu 31 Dec: London peaked at 35.0p at 16:30 (Agile's 35p cap), average 15.1p, lowest 10.3p at 04:30; highest anywhere 35.0p in Eastern England.
• Sat 2 Jan: London peaked at 35.0p at 17:00 (Agile's 35p cap), average 14.8p, lowest 9.2p at 05:00; highest anywhere 35.0p in Eastern England.

Likely causes

• Tue 29 Dec, 16:30 (London's peak): wind 5.5GW (13% of supply), solar 0GW, gas 22.1GW (52%), imports 3.9GW, total supply 42.8GW. Over the day wind averaged 5.3GW; the 2020 average was 7.8GW (25%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Wed 30 Dec, 16:30 (London's peak): wind 3.6GW (8% of supply), solar 0GW, gas 22.7GW (52%), imports 3GW, total supply 43.5GW. Over the day wind averaged 4.3GW; the 2020 average was 7.8GW (25%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Thu 31 Dec, 16:30 (London's peak): wind 5.2GW (12% of supply), solar 0GW, gas 21.6GW (50%), imports 3.9GW, total supply 43.2GW. Over the day wind averaged 4.6GW; the 2020 average was 7.8GW (25%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Sat 2 Jan, 17:00 (London's peak): wind 4.8GW (11% of supply), solar 0GW, gas 22.2GW (51%), imports 3GW, total supply 43.2GW. Over the day wind averaged 4.7GW; the 2021 average was 7.1GW (22%). 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 Wed 30 Dec (3.6GW, against 7.8GW for the year), so gas made up the gap. (inference from NESO data)
• The peak came in the early evening on Tue 29 Dec, Wed 30 Dec, Thu 31 Dec and Sat 2 Jan, when demand is highest and there is no solar. (inference)
• Sat 2 Jan was at the weekend, when demand is usually lower, so high prices then are less expected. (inference)
• Elexon market index: Tue 29 Dec averaged £69.04/MWh with a high of £118.53 at 17:30; Wed 30 Dec averaged £71.60/MWh with a high of £145.97 at 17:30; Thu 31 Dec averaged £63.34/MWh with a high of £86.48 at 16:30; Sat 2 Jan averaged £59.34/MWh with a high of £103.78 at 17:30. Source: Elexon market index, Tue 29 Dec. (confirmed by source; a short-term index, not the day-ahead auction Agile follows)

Wider context that week

• Storm Bella (Sat 26 Dec to Sun 27 Dec) was within a few days of it. Source: Met Office, UK storm season 2020/21. (confirmed by source; its effect on these prices is inference)

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.