Energy was last better‑than‑free: yesterday Next

Research notes

Figures are for London unless they say otherwise.

What happened

• Tue 23 Jun: London averaged 26.1p, with a minimum of 15.0p and a peak of 58.4p at 18:30. Highest anywhere 68.3p in Northern Scotland.
• Wed 24 Jun: London averaged 31.2p and peaked at 76.5p at 21:00, unusually late. Highest anywhere 92.5p in Northern Scotland, the highest price of the half-year and not far below the 100p cap.

Likely causes

• Record June heat. The Met Office issued a red extreme heat warning for Wed 24 and Thu 25 Jun, forecasting 38°C and that the UK June record (35.6°C, Southampton, 1976) would very likely fall. It did: England reached 37.7°C at Lingwood, Norfolk on 26 Jun and Wales 35.9°C in Cardiff on 25 Jun, with over 150 stations setting June records. (confirmed by source) Met Office warning, Met Office recap, 30 Jun 2026
• Very little wind. Wind fell to about 4.3 GW on 23 Jun, and on 24 Jun wind met "only around 10 per cent of demand" with gas plant running near 14.4 GW. (confirmed by source) Prestige, 23 Jun 2026, Prestige, 25 Jun 2026
• NESO issued an Electricity Margin Notice on the evening of Tue 23 Jun for Wednesday's evening peak, and withdrew it on Wednesday afternoon. NESO's own explanation: unusually high temperatures, and "wind and gas generation availability was lower than expected". Osborne Clarke reports NESO confirming it was the first EMN since Jan 2025 "and the first ever issued in the summer period". (confirmed by source) NESO blog, 24 Jun 2026, Osborne Clarke, 2 Jul 2026
• Day-ahead prices: baseload for Tue 23 Jun was £124.16/MWh, and for Wed 24 Jun it settled at £167.13/MWh. The broker lists the causes for the jump as "thin wind, gas supplying around 39 per cent of the GB mix, French nuclear curtailments on high river temperatures, a heavy UK reactor outage schedule and a demand spike around the England versus Ghana match", with the balancing price spiking to £800/MWh. The report does not say so, but this would be the World Cup group game; check the kick-off time before using it. (confirmed by source, apart from the World Cup detail) Prestige, 24 Jun 2026
• AleaSoft gives the GB daily average on 24 Jun as €184.65/MWh, the highest since Jan 2025. Inspired PLC says the day-ahead auction reached 46.8p/kWh in Wednesday's evening peak, and that the price set on Tuesday was the highest for eighteen months. (confirmed by source) AleaSoft, 29 Jun 2026, Inspired PLC, 25 Jun 2026
• French nuclear output was cut by the heat (EDF curtailed about 3 GW, and the 1.3 GW Golfech 2 reactor was halted for a week), so France had less to export. GB was still importing about 12% of demand. Montel adds that "new precautionary trading limits reduced available import capacity just as the June heatwave increased the need for it", and that gas plant output falls in high temperatures. (confirmed by source) Prestige, 23 Jun, Inspired PLC, Montel GB electricity market summary Q2 2026
• The 21:00 peak on 24 Jun is the summer pattern: solar has gone, air conditioning and evening demand have not, and there was no wind to take over. (inference, consistent with Montel's description of "solar coming off" into the evening peak)
• Gas was not the cause. NBP was falling that week (about 102p/therm on Tuesday, 98.65p on Wednesday) as Hormuz traffic recovered. TTF hit its lowest since 21 Apr on 25 Jun. (confirmed by source) Prestige, 24 Jun, AleaSoft, 29 Jun

Wider context that week

• NESO arranged a short-notice trade with France's RTE to cover a shortfall, and worked with neighbouring system operators under "existing arrangements that allow coordinated action during exceptional system conditions". Prestige, 25 Jun, NESO blog
• A US-Iran framework agreement and the reopening of the Strait of Hormuz were unwinding the risk premium in gas and oil all week. Brent fell to about $74/bbl. Prestige, 23 Jun, Prestige, 25 Jun
• The heatwave ran 19 to 28 Jun, with red heat-health alerts for six regions on 24 to 26 Jun. Wikipedia: 2026 United Kingdom heatwaves
• The 13% price cap rise to £1,862 took effect the following week, on 1 Jul. Ofgem
• Bloomberg's 11 Aug headline, "UK Power Price Hits Highest Since June as Temperature Soars", confirms late June as the summer's benchmark spike. (headline and snippet only) Bloomberg

Confidence

High. NESO, the Met Office and three market sources all describe these two days.

Gaps and conflicts

• The cost of emergency imports differs by source: Inspired says imports from the Netherlands reached £1,379/MWh; energynews.pro says NESO paid €1,652/MWh (about £1,400) for 1.7 GW and spent about £10m in hours; the broker says the balancing price spiked to £800/MWh. These may be different trades or different measures. Don't quote one as "the" figure. energynews.pro, 25 Jun 2026
• Forecast temperature: the Met Office said 38°C. Inspired says "forecast to reach 40°C" and Montel says "temperatures above 40°C". The Met Office's provisional maximum was 37.7°C (Wikipedia has 38.0°C). Use the Met Office.
• The day-ahead figure for 24 Jun delivery is £167.13/MWh (broker), about £157/MWh (Inspired, and the broker's "offered around £157" in early trade) or €184.65 (AleaSoft, roughly £159). These are probably different auctions and an early indication against a final settlement.
• "Highest since" also varies: eighteen months (Inspired) or since Jan 2025 (AleaSoft). Both point to the Jan 2025 cold snap.