Negative prices (lockdown, midday sun)
Mon 20 Apr · Tue 21 Apr · Wed 22 Apr
Research notes
Figures are for London unless they say otherwise.
What happened
- Mon 20 Apr: London was below zero for 5 hours (longest spell 3.5 hours from 12:30), min −4.0p at 14:00; average 3.7p, peak 18.9p at 18:30; all 14 regions at 0p or below; lowest −4.8p in Northern Scotland.
- Tue 21 Apr: London was below zero for 8 hours (longest spell 7 hours from 09:00), min −3.1p at 12:30; average 2.9p, peak 20.4p at 18:30; all 14 regions at 0p or below; lowest −3.8p in Northern Scotland.
- Wed 22 Apr: London was below zero for 2.5 hours (longest spell 2 hours from 13:30), min −0.8p at 01:00; average 5.2p, peak 18.9p at 17:30; all 14 regions at 0p or below; lowest −1.0p in Northern Scotland.
Likely causes
- Octopus's lockdown post, updated on 22 Apr 2020, describes negative Agile prices in this period. Source: Octopus Energy blog, 8 Apr 2020. (confirmed by source)
- Mon 20 Apr, 14:00 (London's lowest half-hour): wind 11.6GW (33% of supply), solar 9.2GW, gas 6.2GW (18%), imports 0.7GW, total supply 34.7GW. Over the day wind averaged 11.7GW; the 2020 average was 7.8GW (25%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Tue 21 Apr, 12:30 (London's lowest half-hour): wind 12.4GW (35% of supply), solar 9.5GW, gas 6.4GW (18%), imports 0.8GW, total supply 36.1GW. 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)
- Wed 22 Apr, 01:00 (London's lowest half-hour): wind 10.4GW (45% of supply), solar 0GW, gas 3.9GW (17%), imports 1.6GW, total supply 22.9GW. Over the day wind averaged 8.5GW; 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 Mon 20 Apr and Tue 21 Apr, with solar at 9.2GW and 9.5GW. (inference from NESO data)
- The low came overnight on Wed 22 Apr, when demand is at its lowest (total supply as low as 22.9GW, against a 2020 average of 31.4GW). (inference)
- Elexon market index: Mon 20 Apr averaged £6.51/MWh with a low of −£31.80 at 14:30; Tue 21 Apr averaged £11.01/MWh with a low of −£35.23 at 15:30; Wed 22 Apr averaged £27.20/MWh with a low of £3.00 at 03:30. Source: Elexon market index, Mon 20 Apr. (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
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.