Negative prices (Easter Monday)
Mon 10 Apr · Tue 11 Apr
Research notes
Figures are for London unless they say otherwise.
What happened
- Mon 10 Apr: London was below zero for half an hour from 23:30, min −2.4p at 23:30; average 14.7p, peak 35.8p at 18:00; all 14 regions at 0p or below; lowest −2.9p in Northern Scotland.
- Tue 11 Apr: London was below zero for 2.5 hours (longest spell 1.5 hours from 00:00), min −5.5p at 01:00; average 17.8p, peak 35.8p at 17:30; all 14 regions at 0p or below; lowest −6.6p in Northern Scotland.
Likely causes
- Electric Insights: "April 10th saw negative power prices for most of the day due to an abundance of wind and solar generation." Source: Electric Insights, Q2 2023 introduction. (confirmed by source)
- Mon 10 Apr 2023 was Easter Monday. Source: GOV.UK bank holidays. (confirmed by source)
- Mon 10 Apr, 23:30 (London's lowest half-hour): wind 15.6GW (59% of supply), solar 0GW, gas 3GW (11%), imports 1.7GW, total supply 26.7GW. Over the day wind averaged 14.5GW; the 2023 average was 9GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Tue 11 Apr, 01:00 (London's lowest half-hour): wind 15.5GW (57% of supply), solar 0GW, gas 4.4GW (16%), imports 0.7GW, total supply 27.3GW. Over the day wind averaged 14.7GW; the 2023 average was 9GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- The low came overnight on Mon 10 Apr and Tue 11 Apr, when demand is at its lowest. (inference)
- Mon 10 Apr was a bank holiday (Easter Monday), when demand is lower. (inference)
- Elexon market index: Mon 10 Apr averaged £13.05/MWh with a low of −£59.12 at 15:00; Tue 11 Apr averaged £83.35/MWh with a low of −£13.14 at 01:00. Source: Elexon market index, Mon 10 Apr. (confirmed by source; a short-term index, not the day-ahead auction Agile follows)
Wider context that week
- The Energy Price Guarantee began on 1 Oct 2022, setting household electricity unit rates at 34.0p/kWh. Source: Solar Power Portal, 2022. Octopus applied it to Agile by charging 34p for any half-hour priced 34p to 52p before VAT and taking 17p off anything above, which is why so many half-hours from then to 30 Jun 2023 sit at exactly 35.8p (34p with VAT) and the highest at 82.1p. (confirmed by data in the site's store; see
src/lib/events.mjs) - Storm Noa affected the UK on 12 Apr 2023. Source: Met Office, UK storm season 2022/23.
Confidence
High.
Gaps
- Elexon's system warnings feed has no entries before mid-2023, so warnings for these days couldn't be checked there.