Slightly negative in the afternoon
Research notes
Figures are for London unless they say otherwise.
What happened
London dipped to −1.4p at 14:30, below zero for 1.5 hours. Average 11.2p, evening peak 29.6p. Lowest regional price −1.4p in the East Midlands.
Likely causes
- A one-day wind surge. For delivery on 4 Jun, "UK day-ahead baseload settled sharply lower at 67.79 £/MWh, down by about £29, as wind generation surged by roughly 153 per cent day-on-day and cut gas-fired output by around 67 per cent, more than offsetting a 27 per cent drop in solar." The next report adds that "Wind supplied close to half of Thursday's generation and renewables around two-thirds." (confirmed by source) Prestige, 4 Jun 2026, Prestige, 5 Jun 2026
- A same-day write-up says the GB wholesale price "collapsed to roughly £0.11/MWh" that afternoon, with wind about 45% of the mix, renewables about 70% and demand around 22 GW. It also notes GB was importing about 5.9 GW at the time. (confirmed by source, but a small independent site) EnergyPrices.net, 4 Jun 2026
- That £0.11/MWh figure matters for a post: the wholesale price was about zero, not negative. Agile only went below zero (−1.4p) because of the 3.5p/kWh reduction applied since 1 Apr. (inference from the two sourced figures) Octopus: Agile pricing explained
Wider context that week
- The surge was brief: day-ahead baseload for Fri 5 Jun was back to £101.42/MWh "as the strong midweek wind faded and reduced nuclear output increased reliance on gas-fired generation". Prestige, 5 Jun 2026
- Five of the UK's nine reactors were offline at points in June, including both Sizewell B units. Prestige, 4 Jun 2026
- TTF gas was €47.6 to €49.1/MWh, supported by "increase in hostilities in the Middle East" and stalled US-Iran talks. AleaSoft, 8 Jun 2026
- Ofgem had announced on Wed 27 May that the price cap would rise 13% to £1,862 from 1 Jul, blaming higher wholesale gas prices from the Middle East conflict. Ofgem
Confidence
High. Two sources describe the day itself and agree.
Gaps
- No NESO or mainstream press coverage found.