Negative prices (New Year's Eve gales)
Research notes
Figures are for London unless they say otherwise.
What happened
- London was negative for two half-hours, the deeper at 22:30: −4.2p, the lowest London price of the quarter (−5.0p in Northern Scotland). Daily average 12.2p.
Likely causes
- Very windy day across the UK. The Met Office warned on 29 Dec of gusts up to 65 to 75mph in exposed parts of England and Wales on 31 Dec and 1 Jan, with snow and heavy rain further north. Source: Met Office, 29 Dec. (confirmed by source)
- NESO data: wind averaged 20.0GW (58% of supply), peaked at 21.8GW at 17:00 and was still 20.1GW (62%) at 22:30. Source: NESO historic generation mix. Figures (confirmed by source); link to price (inference).
- Holiday demand. Late evening on New Year's Eve, with most workplaces closed, is about as quiet as a winter evening gets; total supply at 22:30 was 32.4GW and the day's peak was only 39.9GW against 44GW to 45GW in mid-December. Source: NESO historic generation mix. (inference)
- The Elexon Market Index Price fell to −£10.54/MWh at 05:00 and averaged £30.30 for the day. Source: Elexon market index, 31 Dec. (confirmed by source)
Wider context that week
- The Russia to Ukraine gas transit deal expired at the end of the day and flows stopped on the morning of 1 Jan 2025, ending a route that had run for decades. This had been propping up gas prices for weeks. NPR, Bruegel, S&P Global
- The Ofgem cap rose to £1,738 the next morning, 1 Jan 2025. Ofgem summary letter (PDF)
- NESO's year-end figures, published a week later, showed wind as Britain's largest source of electricity for a full year for the first time. New Civil Engineer, 8 Jan 2025
- A good contrast for a post: January 2025's London average was 25.9p, the dearest month in the site's monthly averages file, and 8 Jan 2025 brought the winter's tightest day.
Confidence
Medium to high. Met Office warnings for the day and strong, steady wind in the data, on a holiday evening. No press report specifically about New Year's Eve prices.
Gaps
I recall weather disrupting New Year's Eve events in Scotland but did not verify it, so it is left out. Found no market report for 31 Dec day-ahead prices.