Energy was last better‑than‑free: yesterday Next

Research notes

Figures are for London unless they say otherwise.

What happened

• Fri 22 May: London was below zero for 4.5 hours (longest spell 2.5 hours from 13:30), min −2.9p at 15:00; average 3.3p, peak 17.0p at 17:30; all 14 regions at 0p or below; lowest −3.5p in Northern Scotland.
• Sat 23 May: London was below zero for 12.5 hours (longest spell 7.5 hours from 01:30), min −10.3p at 14:30; average −0.9p, peak 13.7p at 17:30; all 14 regions at 0p or below; lowest −12.3p in Northern Scotland.
• Sun 24 May: London was below zero for 11.5 hours (longest spell 8.5 hours from 01:30), min −4.8p at 07:00; average 3.2p, peak 20.4p at 17:30; all 14 regions at 0p or below; lowest −5.7p in Northern Scotland.

Likely causes

• Elexon: "On 22 May 2020 there were 28 Settlement Periods within the day, which had negative System Prices", the first time since April 2001 that system prices were negative for so much of a day. Source: Elexon: negative system prices during COVID-19. (confirmed by source; system prices, not day-ahead)
• Mon 25 May 2020 was the spring bank holiday, so this was the start of a long weekend. Source: GOV.UK bank holidays. (confirmed by source)
• Electric Insights: wholesale prices averaged just £22/MWh over May 2020, and solar averaged a record 2.7GW over the month. Sources: Electric Insights, Electricity prices plummet (Q2 2020), Electric Insights, Solar eclipses coal (Q2 2020). (confirmed by source)
• Fri 22 May, 15:00 (London's lowest half-hour): wind 12.1GW (37% of supply), solar 7.3GW, gas 6.6GW (20%), imports 0.3GW, total supply 33GW. Over the day wind averaged 11.9GW; the 2020 average was 7.8GW (25%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Sat 23 May, 14:30 (London's lowest half-hour): wind 13GW (42% of supply), solar 6.5GW, gas 4.8GW (15%), imports 0.1GW, total supply 30.8GW. Over the day wind averaged 12.4GW; the 2020 average was 7.8GW (25%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• Sun 24 May, 07:00 (London's lowest half-hour): wind 11.3GW (48% of supply), solar 1.4GW, gas 3.3GW (14%), imports 0.6GW, total supply 23.5GW. Over the day wind averaged 9.9GW; the 2020 average was 7.8GW (25%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
• The low came around midday on Fri 22 May and Sat 23 May, with solar at 7.3GW and 6.5GW. (inference from NESO data)
• Sat 23 May and Sun 24 May were at the weekend, when demand is lower. (inference)
• Elexon market index: Fri 22 May averaged −£10.16/MWh with a low of −£53.02 at 05:00; Sat 23 May averaged £12.38/MWh with a low of −£7.27 at 16:00; Sun 24 May averaged £0.09/MWh with a low of −£36.28 at 09:00. Source: Elexon market index, Fri 22 May. (confirmed by source; a short-term index, not the day-ahead auction Agile follows)

Wider context that week

• The first national lockdown in England began on 23 Mar 2020 ("stay at home"); people who couldn't work from home were asked to return from 10 May, non-essential shops reopened on 15 Jun, and pubs and restaurants on 4 Jul. Source: GOV.UK, timeline of COVID-19 restrictions in 2020 (PDF). (confirmed by source)
• Elexon found that GB electricity demand was 19% lower in Apr and May 2020 than a year earlier, "driven by the COVID-19 lockdown measures", and that 83% of the year's negative system prices to June fell in April and May. Source: Elexon: negative system prices during COVID-19, last updated 29 Jun 2020. (confirmed by source; these are system prices, not the day-ahead prices Agile follows)

Confidence

High. Elexon names 22 May as the most negative day of lockdown; Agile’s −10.3p on 23 May was its lowest to that date.

Gaps

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