Prices touch zero
Thu 18 Dec · Fri 19 Dec
Research notes
Figures are for London unless they say otherwise.
What happened
- Thu 18 Dec: London touched exactly 0.0p at 22:30 but never went below; average 14.7p.
- Fri 19 Dec: two negative half-hours just after midnight, low −0.2p at 00:00; average 14.0p. All 14 regions at or below zero. This is one event: a single windy night spanning midnight.
Likely causes
- A windy, mild, wet spell. The Met Office forecast for Thu 18 Dec said "winds will remain brisk", with highs of 11 to 13°C in the south and rain warnings in force; its week-ahead said south-westerly winds would keep it mild. Mild weather means lower heating demand. (confirmed by source: Met Office daily weather, 17 Dec; Met Office week ahead, 16 Dec)
- Elexon-metered wind averaged 14.7GW on Thu and was 15.5GW at 22:00 as demand fell away for the night. Gas dropped to 3.2GW. (confirmed by source: Elexon FUELHH, 18 to 19 Dec)
- Imports were unusually heavy at the same time, 7.0 to 7.7GW between 20:00 and 22:00. That suggests power was very cheap on the continent too and was flowing into GB on top of the wind. (import figures confirmed by source: same Elexon query; the reading of them is inference)
- Negative prices are rarer in Dec because demand is high, which is why this only just reached zero and only late at night. (inference)
Wider context that week
- European gas had fallen to about €28/MWh at the start of Dec, its lowest since Apr 2024, on Ukraine peace talks, record US LNG exports and mild forecasts. I did not check the price on 18 Dec itself. Cheap gas pulls the whole Agile curve down (inference). (Euronews, 4 Dec 2025; OilPrice)
- NESO's all-time wind record was set a fortnight earlier: 23,825MW at 17:30 on 5 Dec, 47.4% of demand. (Reuters via TradingView)
- Storm Bram had passed on 8 to 11 Dec; there was no named storm on 18 or 19 Dec. (Wikipedia)
Confidence
Medium. The wind, the mild weather and the imports are all in the data, but this was a marginal event and nobody reported on it, so there is no outside confirmation of why the price reached zero.
Gaps
No news report. I did not check continental day-ahead prices for 18 Dec, so "cheap on the continent" is a reading of the import flows, not a sourced fact.