Negative prices
Thu 4 Jul · Fri 5 Jul · Sat 6 Jul
Research notes
Figures are for London unless they say otherwise.
What happened
- Thu 4 Jul: London was below zero for 9.5 hours (longest spell 6.5 hours from 09:30), min −2.3p at 13:30; average 3.5p, peak 19.3p at 18:30; all 14 regions at 0p or below; lowest −2.7p in Northern Scotland.
- Fri 5 Jul: London was below zero for 1 hour (longest spell half an hour from 00:30), min −1.9p at 00:30; average 14.2p, peak 33.8p at 17:30; all 14 regions at 0p or below; lowest −2.2p in Northern Scotland.
- Sat 6 Jul: London was below zero for 3.5 hours from 12:30, min −3.8p at 14:30; average 10.2p, peak 19.1p at 18:30; all 14 regions at 0p or below; lowest −4.5p in Northern Scotland.
Likely causes
- Thu 4 Jul, 13:30 (London's lowest half-hour): wind 17.7GW (47% of supply), solar 9.2GW, gas 2.2GW (6%), imports 1.4GW, total supply 37.3GW. Over the day wind averaged 16.8GW; the 2024 average was 9.4GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Fri 5 Jul, 00:30 (London's lowest half-hour): wind 15.8GW (62% of supply), solar 0GW, gas 3.1GW (12%), imports 0.5GW, total supply 25.5GW. Over the day wind averaged 10GW; the 2024 average was 9.4GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Sat 6 Jul, 14:30 (London's lowest half-hour): wind 9.9GW (31% of supply), solar 7.9GW, gas 2.2GW (7%), imports 5.1GW, total supply 31.6GW. Over the day wind averaged 7.8GW; the 2024 average was 9.4GW (29%). Source: NESO historic generation mix. (figures confirmed by source; link to prices is inference)
- Wind was well above its yearly average at the lowest half-hour on Thu 4 Jul (17.7GW, against 9.4GW for the year). (inference from NESO data)
- The low came around midday on Thu 4 Jul and Sat 6 Jul, with solar at 9.2GW and 7.9GW. (inference from NESO data)
- The low came overnight on Fri 5 Jul, when demand is at its lowest (total supply as low as 25.5GW, against a 2024 average of 32GW). (inference)
- Sat 6 Jul was at the weekend, when demand is lower. (inference)
- Elexon market index: Thu 4 Jul averaged £9.18/MWh with a low of −£13.68 at 05:00; Fri 5 Jul averaged £54.67/MWh with a low of −£2.70 at 01:00; Sat 6 Jul averaged £63.25/MWh with a low of £31.42 at 00:30. Source: Elexon market index, Thu 4 Jul. (confirmed by source; a short-term index, not the day-ahead auction Agile follows)
Wider context that week
- Thu 4 Jul 2024 was the day of the general election. (not checked against a source here; no link to prices is suggested)
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.