02What's flowing through the wires?
When solar peaks, who turns down
When solar peaks at midday, how far do the plants that can turn down go, and at what price?
In France, between 1 March 2026 and 30 June 2026, the nuclear fleet's output between 10:00 and 16:00 sat at least 10% of the same day's peak below it on 113 of 122 complete days, with a mean midday dip of 5.6 GW, an estimate that takes each day's peak as the capacity available that day (ENTSO-E).
The day-ahead price in those midday hours sat at or below €0/MWh in 212 of 732 hours.
The record covers 1 of 6 bidding zone in full so far, and every fuel a plant can turn down on purpose: nuclear, lignite, hard coal, gas, hydro.
A reactor, a coal unit, a gas turbine and a hydro dam can all turn down when solar output peaks. Whether they do, and how far, is in the hourly record. Pick a zone and a fuel.
What turning down costs
A plant that can turn down on purpose is called dispatchable. When solar output peaks the midday price dips, sometimes below zero, and each of these plants decides whether to follow. The first chart shows what the fleet did, hour by hour, for the zone and fuel chosen; the dip at noon is the ramp-down.
The cost differs by fuel. A coal or gas plant saves fuel and carbon, and keeps a unit on standby that earns only when it runs. A reactor saves almost nothing, so every hour it gives up makes the rest dearer. A dam keeps its water for the evening, which is storage. The readings under the charts give each its own figure.
The energy run below the peak is an estimate: each day's highest hour stands in for the capacity available that day, so a unit taken off for maintenance after breakfast counts as a ramp-down too. The method note has the rule and its known false positives.
How these numbers are made: The canonical hourly grid, The midday ramp-down of dispatchable plants.
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