ENTSO-E data carried by euenergy.live logged the France-Germany day-ahead spread hit EUR 93.68/MWh on Wednesday 3 June, the largest single-day print of the series. That is more than double the EUR 46.58 high of 21 May and a clean doubling of the EUR 23.68 compression on 12 May . The sequence of highs is not random volatility; it is the nuclear-versus-gas gradient amplified each time weather pushes renewable output into a grid with nowhere to put it.
Weather provided the trigger. A late-May heatwave that ran French national average temperature to 24.9C on 26 May 1 pushed a midday solar surge into a market where French nuclear was already running 3.1 TWh above the 2025 year-to-date pace, with EDF holding full-year guidance at 350-370 TWh . Germany, short of nuclear and dispatching on gas-plus-carbon, cleared the same demand at EUR 102.64, its second EUR 100-plus print in three weeks.
The VNU (Vente Nucleaire Universelle, the regulated nuclear-pricing scheme that replaced ARENH on 1 January 2026) sharpens the spread into a P&L gap. It passes near-spot power to French industrials . On 3 June that meant a French smelter buying at single digits while a German competitor paid the gas-set clear above EUR 100. That gap does not require a view on energy markets; it is the current cost of running a plant.
The forward calendar narrows the French cushion. From September, the Flamanville-3 reactor (a European Pressurised Reactor, EPR) enters a one-year overhaul that removes 1.6 GW at heating-season onset . The surplus that amplified the heatwave spread is the same surplus the maintenance schedule withdraws into winter, when German gas demand rises and VNU buyers lose the nuclear floor.
