Negative prices overnight, record wind
Research notes
Figures are for London unless they say otherwise.
What happened
London dipped to −0.2p at 04:00 and was below zero for 2 hours (longest spell 1 hour from 03:30). The average was 10.3p and the peak 40.3p at 18:30. All 14 regions went to zero or below, lowest −0.3p in Northern Scotland.
Likely causes
- Britain set a new all-time wind generation record that day: 23,880 MW between 13:30 and 14:00 on 25 Mar, beating 23,825 MW from 5 Dec 2025. Wind was supplying 53.5% of electricity at the time and gas fell to 2.3%, its lowest share in nearly two years. (confirmed by source) RenewableUK, 26 Mar 2026, NESO, 24 Apr 2026, Utility Week
- The wind had already arrived the day before: "Day-ahead baseload collapsed on Tuesday, settling at just £40.72/MWh, down nearly £32 from the prior session, as GB wind output surged from 7.9 GW to 21 GW, pushing renewables to around 64 per cent of total output and cutting CCGT utilisation to roughly 8 per cent." On Wed 25 Mar wind ran at about 21.6 GW (56% of the mix) with gas plants at just 2.4 GW. (confirmed by source) Prestige, 25 Mar 2026, Prestige, 26 Mar 2026
- The GB day-ahead daily average on 25 Mar was €48.12/MWh, the lowest since 2 Jan 2026. (confirmed by source) AleaSoft, 30 Mar 2026
- The negative half-hours were at 03:30 to 04:30, the overnight demand low, not at the time of the afternoon record. (inference from the data)
Wider context that week
- Gas fell sharply on Tue 24 Mar on reports of a US 15-point peace proposal to Iran (NBP from 136p to about 126p/therm), then rebounded on Thu 26 Mar when Iran said it would not negotiate. TTF had peaked near €61/MWh on 19 Mar after Iran's attack on Qatar's Ras Laffan LNG complex. Prestige, 25 Mar, Prestige, 26 Mar
- Carbon Brief's analysis for the month: wind and solar generated a record 11 TWh in Mar 2026 (wind up 38% year on year), avoiding gas imports worth about £1bn while gas cost around 130p/therm because of the Iran war. Carbon Brief
Confidence
High. A NESO-confirmed wind record on the day, with dated price and generation figures.
Gaps
- No named storm was involved (the Met Office used only four names all season), and no source names the weather system.
- One broker report (30 Mar) says the record of about 23.9 GW was reached "on Saturday afternoon", that is 28 Mar. NESO and RenewableUK both say Wed 25 Mar, and they are the authority. Treat the broker line as an error.