Negative prices (clock-change weekend)
Sat 25 Oct · Sun 26 Oct · Mon 27 Oct
Research notes
Figures are for London unless they say otherwise.
What happened
- Sat 25 Oct: below zero for 3 hours overnight, low −0.4p, average 5.4p.
- Sun 26 Oct: below zero for 5 hours, including 3 hours from 02:30, low −4.2p (−5.0p in Northern Scotland), average 8.4p.
- Mon 27 Oct: one negative half-hour at 00:00 (−0.9p), then a normal working day (average 14.6p, peak 36.8p). All 14 regions negative each day.
Likely causes
- The windiest spell of the autumn so far, behind Storm Benjamin. The Met Office said on 23 Oct that cold Arctic air would follow the storm with "brisk northerly winds" over the weekend. (confirmed by source: Met Office, Storm Benjamin pulls away, 23 Oct)
- Elexon-metered wind averaged 16.2GW on Sat 25 Oct, the second-highest daily figure of the whole Sep to Dec period, and 15.5GW on Sun. It never dropped below 15.6GW on Sat. Gas averaged just 2.4GW on Sun. (confirmed by source: Elexon FUELHH, 25 to 27 Oct; ranking is my calculation)
- A record was set. Drax Electric Insights says that on 27 Oct "wind farms came within touching distance of supplying three quarters of the country's electricity demand", a new record share of 74.9%. In the Elexon data wind was 17.2 to 17.5GW in the first hours of Mon 27 Oct with gas at 2.2GW and over 3GW being exported, which is when the 00:00 negative price occurred. (record confirmed by source: Drax Electric Insights Q4 2025, section 7, summary page here; that the record fell in the small hours is inference from Elexon data, since Drax gives the date but not the time)
- Low weekend demand, and the deepest negative prices were in the small hours of Sun when demand is at its lowest. (inference from the same data)
- By Mon evening wind had halved to about 7GW and gas was back at 12.7GW, hence the ordinary Monday peak. (confirmed by source: same Elexon query)
Clock change
- The clocks went back at 02:00 on Sun 26 Oct, so that day had 25 hours (50 half-hours). The −4.2p low is stamped 02:30, right at the changeover. Worth checking how the site displays the repeated hour before quoting that time in a post.
Wider context that week
- Storm Benjamin on Thu 23 Oct (yellow wind and rain warnings for England and Wales). (Met Office)
- US and EU sanctions on Russian energy, 22 and 23 Oct (see previous section).
Confidence
High. Strong, sustained wind in the data, a Met Office forecast that matches, and an independently reported record wind share on 27 Oct.
Gaps
No news report on GB negative prices that weekend. No NESO announcement found for the 27 Oct share record; Drax is the only source.