Negative prices (the first lockdown weekend)
Research notes
Figures are for London unless they say otherwise.
What happened
- Sun 29 Mar: London was below zero for 2.5 hours from 03:00, min −1.1p at 03:00; average 5.4p, peak 20.2p at 18:30; all 14 regions at 0p or below; lowest −1.3p in Northern Scotland.
Likely causes
- The clocks went forward that morning (the last Sunday in March), so the night was an hour short. Source: GOV.UK, when do the clocks change. (confirmed by source; any effect on prices is not established)
- Sun 29 Mar, 03:00 (London's lowest half-hour): wind 12.7GW (52% of supply), solar 0GW, gas 4.4GW (18%), imports 1.6GW, total supply 24.5GW. Over the day wind averaged 11.6GW; 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 29 Mar, when demand is at its lowest (total supply as low as 24.5GW, against a 2020 average of 31.4GW). (inference)
- Sun 29 Mar was at the weekend, when demand is lower. (inference)
- Elexon market index: Sun 29 Mar averaged £18.21/MWh with a low of −£0.55 at 05:00. Source: Elexon market index, Sun 29 Mar. (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.