Negative prices (lockdown)
Sun 10 May · Mon 11 May
Research notes
Figures are for London unless they say otherwise.
What happened
- Sun 10 May: London reached 0p at 06:30 (1 hour at 0p in all); average 4.5p, peak 18.5p at 18:00; all 14 regions at 0p or below; lowest 0.0p in Eastern England.
- Mon 11 May: London was below zero for 3 hours (longest spell 2 hours from 02:30), min −1.5p at 03:30; average 5.9p, peak 20.8p at 18:30; all 14 regions at 0p or below; lowest −1.8p in Northern Scotland.
Likely causes
- Sun 10 May was the day the government asked people who couldn't work from home to go back to work from the next day. (confirmed by source; see the context below)
- Sun 10 May, 06:30 (London's lowest half-hour): wind 8.7GW (41% of supply), solar 0.7GW, gas 4.4GW (20%), imports 0.7GW, total supply 21.3GW. Over the day wind averaged 11.3GW; the 2020 average was 7.8GW (25%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Mon 11 May, 03:30 (London's lowest half-hour): wind 11.6GW (52% of supply), solar 0GW, gas 3.3GW (15%), imports 0.3GW, total supply 22.1GW. Over the day wind averaged 10.9GW; the 2020 average was 7.8GW (25%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- The low came overnight on Sun 10 May and Mon 11 May, when demand is at its lowest (total supply as low as 21.3GW, against a 2020 average of 31.4GW). (inference)
- Sun 10 May was at the weekend, when demand is lower. (inference)
- Elexon market index: Sun 10 May averaged £13.92/MWh with a low of −£4.47 at 23:30; Mon 11 May averaged £13.27/MWh with a low of −£11.95 at 03:30. Source: Elexon market index, Sun 10 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
Low. Neither the grid figures nor any report found clearly explain 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.