July 13 (Reuters) - High river temperatures that look set to restrict power output at two French nuclear plants that use river water to cool reactors may trigger increased fossil fuel-fired power output elsewhere due to Europe's extensive regional power trading.

France regularly exports surplus power from its vast non-emitting nuclear fleet to neighbours Germany, Switzerland, Spain and Italy, and also imports power from the United Kingdom, Germany and elsewhere as a central player in one of the world's most active electricity trading markets.

However, with French nuclear power set to dip from at least two plants that cool reactors off the unusually warm Rhone river, a key source of clean electricity looks set to be withdrawn from Europe's power grids that may need to be replaced by power generated from natural gas or coal plants elsewhere on the continent.

In turn, any increased output from fossil fuel-fired power plants will likely lift regional power sector emissions, undermining regional efforts to accelerate cuts to all forms of industrial pollution.


France has one of the world's most nuclear-dependent energy systems, with 56 nuclear reactors generating around 70% of the country's electricity, according to data from the International Atomic Energy Agency and Ember.

France is also Europe's second largest electricity generator behind Germany, producing roughly 470 terawatt hours (TWh) of electricity in 2022, compared to Germany's 582TWh, and 324TWh by Europe's third largest generator, the United Kingdom.

France's high proportion of non-emitting nuclear power means that its power sector has by far the lowest carbon intensity of any major European economy, averaging around 85 grams of carbon dioxide per kilowatt hour of electricity produced.

That compares to more than 385 grams in Germany, 257 in the United Kingdom, and 300 for Europe as a whole, Ember data shows.

In addition, France has land borders with Belgium, Luxembourg, Germany, Switzerland, Italy and Spain, as well as a maritime border with the United Kingdom, making it an ideal electricity trading partner for all of those nations.

However, with domestic nuclear output set to be constrained for at least the coming days, according to the country's main power operator EDF, France will have reduced electricity supplies available for export that may have a knock-on effect for power consumers elsewhere in the region.


Italy, Switzerland and the United Kingdom were the largest importers of French power in 2022, while Germany, Belgium and Spain were the top net trade partners, according to France's electricity transmission operator RTE.

To make up for any shortfall in supplies from France, each nation may opt to dial up domestic generation or boost power imports, or both.

However, power producers will likely have already lifted output recently as each nation grapples with increased demand from higher use of air conditioners during the spell of above-normal temperatures across continental Europe.

That could mean that utilities may have limited scope to boost output further without resorting to increased use of fossil fuel-fired plants that generate emissions alongside the power they create.

Most utilities across Europe will also deploy quickly rising volumes of renewable power across their grids, and many will have brought additional green power capacity online within the past year.

But as no other European power producer can match France for scale in terms of clean power heft, any sustained dips in output from France will likely be plugged by extra fossil fuel-powered generation elsewhere - until France's rivers cool enough to allow its nuclear fleet to crank back up.

(Reporting By Gavin Maguire; Editing by Jamie Freed)