Negative prices (sunny, breezy spell)
Thu 3 Apr · Sat 5 Apr
Research notes
Figures are for London unless they say otherwise.
What happened
3 Apr: a single half-hour at −0.1p at 14:00 (London), on a weekday. 5 Apr: London down to −3.8p at 12:30 and below zero for 4.5 hours from 11:30; all regions negative, lowest −4.5p in Northern Scotland.
Likely causes
- Near-record solar on both days. PV_Live puts the solar peak at about 12.5GW on 3 Apr and about 13.3GW on 5 Apr, both in the early afternoon. (confirmed by source: grid data) PV_Live 3 Apr · PV_Live 5 Apr
- Steady wind at the same time: transmission-metered wind averaged 10.4GW on 3 Apr and 8.7GW on 5 Apr. Gas fell to about 1.9GW and 1.7GW at the low points. On 5 Apr GB tipped into net exports mid-afternoon. (confirmed by source: grid data) Elexon FUELHH 3 to 5 Apr 2025
- 5 Apr was a Saturday, so demand was lower, which is why it went properly negative while Thursday only touched zero. (inference)
- The solar record fell the next day, Sun 6 Apr: 12.68GW by NESO's measure, 13.2GW at 13:00 by Sheffield Solar's, meeting 40% of demand. The two figures differ because the bodies measure differently; one later round-up quotes 13.8GW, which I could not reconcile. (confirmed by source, figures differ) Carbon Brief, 4 Jun 2025 · NESO Summer Outlook news, 15 Apr 2025 · Solar Power Portal 2025 round-up
- High pressure sat over the UK for the first two weeks of April, in what became the sunniest April on record. (confirmed by source) Met Office, 30 Apr 2025
Wider context that week
- US "liberation day" tariffs were announced on 2 Apr. European gas fell sharply with wider markets in the following days, to a seven-month low by 9 Apr, on fears for demand and hopes of more LNG heading to Europe. Cheaper gas lowers the whole Agile curve, not just the midday dip. Bloomberg, 9 Apr 2025 (paywalled, headline and summary only) · Natural Gas Intelligence (blocked to automated access, not read directly)
- New price cap (£1,849) in force from 1 Apr. Ofgem
Confidence
Medium to high. The grid data explains both days well. No news source discusses either date.
Gaps
No report found of negative wholesale prices on 3 or 5 Apr. Argus says the N2EX hourly day-ahead auction had only four negative hours in the whole of April 2025, yet Agile shows about 9.5 hours at or below zero across 3, 5 and 27 Apr. I did not establish why; it may be down to which auction Agile is priced from. Worth checking before a post states "wholesale prices went negative for X hours". Argus, 27 May 2025