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Europe's grid restructures around renewable generation

Europe's grid restructures around renewable generation

Built World

France's nuclear fleet now bends for solar, the clearest data yet that the continent's power system is being rebuilt around variable supply

May 14th, 2026: PV Magazine and Modo Energy publish convergent analyses

Overview

France's 56 reactors were built in the 1980s and 1990s as Europe's steady electricity backbone. New analysis of European Network of Transmission System Operators for Electricity (ENTSO-E) data published May 14 shows they now ramp down each midday to make room for solar.

The midday-to-evening swing in French nuclear output grew nearly eightfold since 2019: from 582 megawatts to 4,426 in peak solar months. Total nuclear modulation hit 33 terawatt-hours in 2025, more than double 2019. The pattern is now appearing in winter too.

Why it matters

Nuclear's role in Europe is shifting from steady producer to grid balancer for solar, changing which plants get built and how power markets price flexibility.

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Key Indicators

8x
Growth in midday output swing since 2019
France's nuclear fleet now ramps 4,426 megawatts between noon and evening, up from 582 megawatts.
33 TWh
Nuclear modulation in 2025
Total energy French reactors held back to make room for cheaper renewable power, double the 2019 figure.
92.3 TWh
Record French net power exports in 2025
France was a net electricity exporter in 98.5% of all hours during the year.
436
Hours of negative wholesale prices in 2025
Periods when European day-ahead prices fell below zero, pushing reactors to cut output.
65%
Nuclear share of French generation in 2024
Down from 78% in 1990 as renewables and changing demand patterns reshape the mix.

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Timeline Five events from this story — drag them oldest to newest. Log in to play
Connections Sixteen names from the news. Find the four hidden groups of four. Log in to play

People Involved

Safa Sen
Safa Sen
Author of the May 14 pv magazine analysis
 Timothée Lauvergne
Timothée Lauvergne
Author of parallel Modo Energy research on French nuclear flexibility

Organizations Involved

Électricité de France (EDF)
Électricité de France (EDF)
State-controlled utility
Operator of France's 56 nuclear reactors

EDF is the French state utility that owns and runs the country's nuclear fleet.
Réseau de Transport d'Électricité (RTE)
Réseau de Transport d'Électricité (RTE)
Transmission system operator
Operates the French high-voltage grid and dispatches generation

RTE runs the French electricity grid and decides which plants ramp up or down each hour.
Autorité de Sûreté Nucléaire (ASN)
Autorité de Sûreté Nucléaire (ASN)
Nuclear safety regulator
Reviews lifetime extensions and operating safety for French reactors

ASN is the French regulator that signs off on whether reactors can keep running.
European Network of Transmission System Operators for Electricity (ENTSO-E)
European Network of Transmission System Operators for Electricity (ENTSO-E)
Industry association
Source of the hourly grid data underlying the analyses

ENTSO-E coordinates Europe's transmission operators and publishes the hourly grid data the analyses rely on.

Timeline

March 1974 May 2026

11 events Latest: May 14th, 2026 · 1 month ago Showing 8 of 11
Tap a bar to jump to that date

  1. PV Magazine and Modo Energy publish convergent analyses

    Latest Analysis

    Safa Sen at Ricardo and Timothée Lauvergne at Modo Energy independently document the eightfold growth in French nuclear's daily ramp since 2019.

  2. Winter modulation appears in Q1 data

    Data

    First-quarter ENTSO-E data shows a midday-to-evening swing of about 2,500 megawatts in winter, when European solar is at its annual minimum.

  3. 2025 totals confirm structural shift

    Data

    French nuclear modulation reaches 33 terawatt-hours, average midday-evening swing 4,426 megawatts. Net exports hit a record 92.3 terawatt-hours.

  4. Cruas plant cuts to 41% as prices go negative

    Market event

    Day-ahead wholesale prices hit minus 50 euros per megawatt-hour. The Cruas reactor reduces output to 41% of capacity to relieve oversupply.

  5. EDF renationalized

    Corporate

    The French state buys out remaining minority shareholders. EDF returns to 100% public ownership amid the corrosion crisis and energy-price spike.

  6. Stress-corrosion cracking grounds half the fleet

    Operational crisis

    EDF discovers cracking in safety-injection piping. Output collapses; France becomes a net power importer for the first time in decades.

  7. Fessenheim plant closes

    Infrastructure

    France's oldest nuclear plant shuts, leaving 56 operating reactors. The closure is political, not flexibility-driven.

  8. Baseline year for French nuclear modulation

    Data

    Average midday-to-evening nuclear swing measures 582 megawatts during the April-September solar window. Total annual modulation: 15 terawatt-hours.

  9. California's duck curve emerges

    Grid pattern

    California Independent System Operator publishes the duck curve, the first major sign that solar is hollowing out midday net demand on a large grid.

  10. French nuclear fleet largely complete

    Infrastructure

    By the late 1990s, France has built 58 reactors providing roughly three-quarters of national electricity. The fleet is designed to run flat as baseload.

  11. France launches the Messmer Plan

    Policy

    After the 1973 oil shock, Prime Minister Pierre Messmer announces a crash program to build out nuclear power as France's electricity backbone.

Historical Context

2 moments from history that rhyme with this story — and how they unfolded.

March 2014

California ISO publishes the duck curve (2014)

The California Independent System Operator released a now-famous chart showing midday net demand sagging as rooftop and utility solar grew. The shape resembled a duck. Gas plants had to cut output around noon and ramp hard at sunset to cover the evening peak.

Then

Operators kept the lights on by running gas peakers harder and cycling combined-cycle units that were not designed for it. Wear and emissions per megawatt-hour rose.

Now

California eventually responded by deploying large-scale battery storage. By 2024 the state had over 10 gigawatts of grid batteries, which now absorb midday solar and discharge into the evening peak.

Why this matters now

France is now living a slower, larger version of the duck curve, but with a nuclear fleet rather than a gas fleet absorbing the swing. The California experience suggests the long-run answer is storage, not endless ramping of plants designed for steady operation.

March 2011 to April 2023

German Energiewende and the death of merchant baseload (2011-2022)

After the Fukushima accident, Germany committed to phase out nuclear and accelerated renewable buildout under the Energiewende. Wholesale prices crashed at midday. Coal and gas plants designed to run flat were forced to cycle daily, then to close.

Then

Major utilities RWE and E.ON took multi-billion-euro writedowns on conventional plants. Several hard-coal stations retired earlier than planned.

Now

Germany rebuilt its market design around capacity mechanisms and flexibility payments. The country now imports power from France during low-renewable periods and exports during sunny windows.

Why this matters now

Germany shows the financial path that follows the operational shift. Once a fleet starts running bent, the merchant economics change. Without new market design, plant owners either lose money or close units. France will face the same question for nuclear.

Sources

(2)
pv magazine International Modo Energy