03Where does power flow, and why do prices split?
France's nuclear: where it sits, who it powers, when it dips
Where does France make its nuclear power, which régions depend on it, and what happens when the fleet dips?
France has 57 nuclear reactors at 18 sites, about 63 GW in all (site data as of 2025, from the French grid operator RTE and the IAEA).
Over the 12 months to 31 August 2026, they made about 68% of the electricity generated in France's régions, and 6 of the 12 régions mapped sent out more power than they used (RTE's éCO2mix).
Centre-Val de Loire sent out the most, about 7.0 GW on average; Île-de-France drew in the most, about 7.2 GW.
Régional generation, consumption and balance come from the French grid operator RTE's éCO2mix via ODRÉ, counted where the power is generated. Nuclear site locations are public; reactor counts and capacity change over time, so the map caption dates its fleet figures.
A handful of large sites on the Loire, the Rhône, the eastern rivers and the north coast power the entire country. Red circles are demand centres; note how much Île-de-France consumes with almost no local generation.
France made a deliberate, state-led bet in the 1970s and 1980s: a large fleet of reactors supplying most of its electricity. The result is a highly centralised, low-carbon grid: a handful of big sites on rivers and the coast power the whole country, the structural opposite of Germany's distributed wind and solar. Wattlas shows where that power is made and which régions lean on it, and takes no position on nuclear policy.
Generation minus consumption by région. Nuclear-dense régions (Centre-Val de Loire, Auvergne-Rhône-Alpes, Normandie, Grand Est) run large surpluses; demand-heavy Île-de-France and generation-poor régions lean on the rest of the country.
France is a single bidding zone: one wholesale price nationwide. A région's surplus or deficit here is a physical balance (generation − consumption); prices stay national, for the same reason Germany's north–south split doesn't show up in prices.
Nuclear output varies through the year. It falls in spring and summer for refuelling and maintenance, which are planned for the lower-demand months. France keeps exporting through the dip (demand drops too, and solar rises), so the seasonal swing rarely strains supply; the sharper risk is heatwaves, when warm rivers limit cooling.
can't always move its wind to the demand
can't always keep its nuclear cool
"Available capacity" is how much of the fleet could run; "output" is how much did. Dips come from planned maintenance and refuelling (concentrated in the lower-demand months), unplanned outages and, in heatwaves, environmental limits on how much warm water reactors may return to rivers, which forces output down. These are operational and environmental limits.
The ranking of technologies by cost depends on what you count.
Plant-level cost is the sticker price. The full system cost adds the costs headline figures leave out (waste and decommissioning, the system cost of running a grid on variable renewables, and implicit public support), applied to every technology alike, and the order shifts. Nuclear's waste and decommissioning are large in total (the Cigéo repository, about €33–37 billion) but small per MWh, and they are provisioned and already in France's official cost figures; whether the provisions are adequate is disputed. Renewables' system costs rise as their share grows. Figures are illustrative central values from published studies (Lazard, Cour des comptes, ANDRA, OECD-NEA, IRENA), each with a wide, assumption-dependent range: curated estimates, updated by hand.
When solar peaks at midday, how far the reactors turn down, and at what price, is on Midday Ramp-down, beside the coal, gas and hydro fleets of the neighbouring zones.
Questions
How many nuclear reactors does France have?
57 reactors at 18 sites, about 63 GW in all, according to site data as of 2025 from RTE, the French grid operator, and the International Atomic Energy Agency (IAEA). Over the 12 months to 31 August 2026, they made about 68% of the electricity generated in France's régions (RTE's éCO2mix).
Which French régions send out the most electricity?
Over the 12 months to 31 August 2026, 6 of the 12 régions mapped sent out more power than they used. Centre-Val de Loire sent out the most, about 7.0 GW on average; Île-de-France drew in the most, about 7.2 GW, according to éCO2mix data from RTE, the French grid operator.
How these numbers are made: The canonical hourly grid.
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