Negative prices (overnight)
Research notes
Figures are for London unless they say otherwise.
What happened
- Fri 7 Oct: London was below zero for half an hour from 05:00, min −2.8p at 05:00; average 24.6p, peak 41.8p at 18:30; all 14 regions at 0p or below; lowest −3.4p in Northern Scotland.
Likely causes
- Fri 7 Oct, 05:00 (London's lowest half-hour): wind 15.7GW (62% of supply), solar 0GW, gas 3.4GW (14%), imports 0.9GW, total supply 25.3GW. Over the day wind averaged 16.6GW; the 2022 average was 8.8GW (27%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- The low came overnight on Fri 7 Oct, when demand is at its lowest (total supply as low as 25.3GW, against a 2022 average of 33.1GW). (inference)
- Elexon market index: Fri 7 Oct averaged £154.02/MWh with a low of −£38.66 at 05:00. Source: Elexon market index, Fri 7 Oct. (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)
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.