Energy was last better‑than‑free: yesterday Next

Research notes

Figures are for London unless they say otherwise.

What happened

• Tue 5 Jan: London peaked at 35.0p at 17:00 (Agile's 35p cap), average 15.1p, lowest 9.2p at 22:30; highest anywhere 35.0p in Eastern England.
• Wed 6 Jan: London peaked at 35.0p at 16:00 (Agile's 35p cap), average 18.2p, lowest 9.2p at 22:30; highest anywhere 35.0p in Eastern England.
• Thu 7 Jan: London peaked at 35.0p at 16:30 (Agile's 35p cap), average 16.8p, lowest 9.9p at 03:30; highest anywhere 35.0p in Eastern England.
• Fri 8 Jan: London peaked at 35.0p at 16:00 (Agile's 35p cap), average 18.6p, lowest 10.5p at 02:30; highest anywhere 35.0p in Eastern England.
• Sat 9 Jan: London peaked at 35.0p at 17:00 (Agile's 35p cap), average 15.2p, lowest 10.5p at 07:00; highest anywhere 35.0p in Eastern England.

Likely causes

• Electric Insights: "On the 6th January there was a predicted shortfall of 0.6 GW capacity, rising to 1.2 GW on both the 8th and 13th of January", and the ESO issued an Electricity Capacity Market Notice on the 8th "for only the third time in its history". It puts this down to unusually cold weather and plant outages, which "created very tight supply margins throughout January". Sources: Electric Insights, Cold weather and tight margins (Q1 2021), Electric Insights, Q1 2021 headlines. (confirmed by source)
• Electric Insights: on the 8th "real-time prices hit a record £4,000/MWh". Source: Electric Insights, Power system records (Q1 2021). (confirmed by source; real-time prices, not the day-ahead prices Agile follows)
• Tue 5 Jan, 17:00 (London's peak): wind 8.9GW (19% of supply), solar 0GW, gas 22.3GW (47%), imports 2.5GW, total supply 47.4GW. Over the day wind averaged 9GW; the 2021 average was 7.1GW (22%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Wed 6 Jan, 16:00 (London's peak): wind 3.9GW (9% of supply), solar 0GW, gas 22.9GW (51%), imports 3.3GW, total supply 44.9GW. Over the day wind averaged 5.1GW; the 2021 average was 7.1GW (22%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Thu 7 Jan, 16:30 (London's peak): wind 4GW (9% of supply), solar 0GW, gas 23.6GW (50%), imports 3.2GW, total supply 47GW. Over the day wind averaged 4.1GW; the 2021 average was 7.1GW (22%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Fri 8 Jan, 16:00 (London's peak): wind 3.4GW (7% of supply), solar 0GW, gas 23.3GW (52%), imports 3.5GW, total supply 44.8GW. Over the day wind averaged 4.1GW; the 2021 average was 7.1GW (22%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Sat 9 Jan, 17:00 (London's peak): wind 7.1GW (16% of supply), solar 0GW, gas 21.9GW (49%), imports 3GW, total supply 45.1GW. Over the day wind averaged 5.6GW; 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 Fri 8 Jan (3.4GW, against 7.1GW for the year), so gas made up the gap. (inference from NESO data)
• The peak came in the early evening on Tue 5 Jan, Wed 6 Jan, Thu 7 Jan, Fri 8 Jan and Sat 9 Jan, when demand is highest and there is no solar. (inference)
• Sat 9 Jan was at the weekend, when demand is usually lower, so high prices then are less expected. (inference)
• Elexon market index: Tue 5 Jan averaged £66.16/MWh with a high of £95.15 at 17:30; Wed 6 Jan averaged £80.03/MWh with a high of £218.43 at 17:30; Thu 7 Jan averaged £116.19/MWh with a high of £595.28 at 17:30; Fri 8 Jan averaged £155.61/MWh with a high of £830.00 at 17:00; Sat 9 Jan averaged £68.98/MWh with a high of £107.72 at 17:00. Source: Elexon market index, Tue 5 Jan. (confirmed by source; a short-term index, not the day-ahead auction Agile follows)

Wider context that week

• Agile was capped at 35p per kWh for new customers until 22 Jul 2022 (the version Agile launched with, AGILE-18-02-21; see src/lib/products.mjs), so a "high" day before then is one where the evening peak reached that cap. (confirmed by data: the capped half-hours sit at exactly 35.0p)
• England's third national lockdown was announced on 4 Jan 2021. (not checked against a GOV.UK source)

Confidence

High. A capacity market notice on the 8th and a published shortfall on the 6th and 8th.

Gaps

• Elexon's system warnings feed has no entries before mid-2023, so warnings for these days couldn't be checked there.