Energy was last better‑than‑free: yesterday Next

Research notes

Figures are for London unless they say otherwise.

What happened

• Sat 10 Sep: London peaked at 78.0p at 16:00 (Agile's 78p cap), average 67.7p, lowest 49.8p at 03:30; highest anywhere 78.0p in Eastern England.
• Sun 11 Sep: London peaked at 78.0p at 16:30 (Agile's 78p cap), average 66.2p, lowest 48.3p at 13:30; highest anywhere 78.0p in Eastern England.

Likely causes

• Sat 10 Sep, 16:00 (London's peak): wind 1.6GW (5% of supply), solar 3.2GW, gas 16.2GW (55%), imports 0.8GW, total supply 29.2GW. Over the day wind averaged 2.8GW; the 2022 average was 8.8GW (27%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Sun 11 Sep, 16:30 (London's peak): wind 5.8GW (18% of supply), solar 2.2GW, gas 15.6GW (49%), imports 0.4GW, total supply 32GW. Over the day wind averaged 4.6GW; the 2022 average was 8.8GW (27%). 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 Sat 10 Sep (1.6GW, against 8.8GW for the year), so gas made up the gap. (inference from NESO data)
• The peak came in the early evening on Sat 10 Sep and Sun 11 Sep, when demand is highest and there is no solar. (inference)
• Sat 10 Sep and Sun 11 Sep were at the weekend, when demand is usually lower, so high prices then are less expected. (inference)
• Elexon market index: Sat 10 Sep averaged £303.60/MWh with a high of £391.53 at 18:00; Sun 11 Sep averaged £287.72/MWh with a high of £363.97 at 17:30. Source: Elexon market index, Sat 10 Sep. (confirmed by source; a short-term index, not the day-ahead auction Agile follows)

Wider context that week

• See the 29 Aug to 1 Sep 2022 event: Electric Insights says wholesale prices were at a record in August and "in freefall since". Source: Electric Insights, Power prices ease going into winter (Q3 2022). (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.
• Elexon's system warnings feed has no entries before mid-2023, so warnings for these days couldn't be checked there.