Heat and power: Impacts of the 2025 heatwave in Europe

Heatwaves have a major impact on European power systems

From economic to energy security challenges, heatwaves bring major disruptions to electricity grids.

1.1 Heatwaves can increase daily power demand by up to 14% and double average prices

During the 2025 heatwave, culminating between June 28 and July 2, peak daily temperatures averaged over the whole country reached 35°C in Germany and Spain (with local maximums exceeding 40°C), 34°C in France and 30°C in Poland. In the most striking case of Germany, this meant a 9°C increase in peak daily temperature compared to just a week before.

This temperature increase had a major impact on electricity demand – which grew by up to 6% in Germany, 9% in France and 14% in Spain, when comparing a Tuesday before (June 24) and during the heatwave (July 1). Peak demand grew as well, by 12% in France and 15% in Spain, and 5% in Germany and Poland.

The demand trends, combined with outages of thermal power plants (described in the following section), led to a dramatic rise of electricity prices. Compared to the same baseline day of June 24, during the heatwave average daily prices grew by 15% in Spain, 106% in Poland, 108% in France and 175% in Germany – in the latter case almost tripling. During peak evening hours on July 1, prices reached over 400 €/MWh in Germany and over 470 €/MWh in Poland.

1.2 Heatwaves elevate the risk of thermal plant outages

Heatwaves impact electricity systems in several ways. The overheating of cables is the likely cause of power outages in Italy on July 1. With rising air and water temperatures, the cooling of thermal power plants becomes more challenging as well. This led to forced reductions in electricity generation from nuclear power plants in France and Switzerland. In Poland, longtime concerns around the cooling of coal power plants led to several remedial actions in the past few years. To further strengthen grid resilience, at the peak of the heatwave on July 2, the government together with the grid operator PSE proposed an anti-blackout package.

The French nuclear fleet has been impacted the most, with all but one of the 18 facilities experiencing some type of capacity reduction. Power plants along the Garonne, Loire and Rhône rivers were impacted the most, with e.g. the Golfech plant having to shut down completely. While multiple reductions were related to scheduled maintenance, at least 7 GW of offline capacity on July 1–2 was marked as “Forced” by the transmission system operator (TSO). Reductions in Bugey 2 and Golfech 1 were marked as “Planned”, but specifically spanned the heatwave period. This means that the heatwave might have impacted up to 15% of France’s nuclear capacity.

1.3 The sun brings heat, but also power

While heatwaves bring major challenges, these are partially offset by the large volumes of solar energy available during daytime. In fact, June 2025 was the highest EU solar electricity production month on record – 45 TWh, a 22% increase from June 2024 (37 TWh).

In the peak days of the heatwave, solar delivered up to 50 GW of power in Germany alone, generating 33–39% of Germany’s electricity. Germany has 14 GW of battery storage and 10 GW of pumped storage, which helped to store some solar to use when the sun went down.

Solar power is one of the cheapest forms of electricity that Europe has. However, when the sun goes down, electricity will naturally be more expensive. Consumers using air conditioning to keep cool during a hot day should have access to cheap electricity. But when the sun goes down, they will need to pay more to use power-hungry AC units. Smart electrification and time of use tariffs can not only unlock consumer savings, but also ease grid balancing at times of stress, such as during a heatwave.

Smart solutions can help with grid stability during extreme weather events

Heatwaves are expected to happen more and more often in Europe. Deploying measures such as clean flexibility and interconnection can help grid operators prepare, and avoid disruptions in the future.

2.1 Heatwaves are set to become more frequent

With climate change accelerating, heatwaves are expected to increase in frequency and intensity. 2025 is likely to become the second hottest year on record, only behind 2024. Multiple records were broken in the June–July heatwave, including mainland Portugal’s record of 46.6°C.

Impacts of extreme weather events on Europe’s power systems are estimated in billions of euros over the next decade, and 45 billion euros in 2023 alone for the wider European economy, according to the European Environment Agency (EEA).

2.2 The widening price spreads during heatwaves show the need for battery storage, clean flexibility and interconnection

While heatwaves are a severe challenge for governments and grid operators, they also present an opportunity for clean flexibility solutions. Due to a high supply of solar electricity during the day, and a cooling-related demand peak in the late afternoon hours, the daily electricity price spreads skyrocketed to over 400 €/MWh on July 1.

This means that matching electricity consumption with generation mattered more than ever. Storage assets benefitted from price spreads, charging at low prices and discharging during expensive peak time, reducing the need for costly imported fossil fuels in the evening, and supporting the balancing of the grid.

Interconnection played a role as well. The heatwave swept across Europe, peaking in Madrid on Sunday, Paris on Tuesday, Berlin and Warsaw on Wednesday – and with that, interconnectors moved electricity to where it was needed most, dissipating the price peaks in the process. In fact after the major blackout earlier in 2025, Spain and Portugal have been calling for more interconnection, to help in stabilizing the grid after potential disruptions – such as ones related to heatwaves.

2.3 Additional solutions can boost grid resilience during extreme weather events

Aside from the deployment of clean flexibility, storage and interconnection, several actions are being taken by European grid operators to plan for times of grid stress, or even blackouts. Some of them are still pilot or R&D projects, but heatwaves like the recent one make a strong case for their wide adoption.

The Distributed ReStart project by the UK National Energy System Operator (NESO) explored how distributed energy sources, including wind and solar, could be used to restart the grid after a blackout. One of the recommendations was to increase the adoption of grid-forming inverters that can start without external voltage supply, building renewables-powered energy islands that are later joined to synchronize the whole grid. Modelling of grid forming assets is tested by the Belgian TSO – Elia, as well.

Several grid-forming solutions are already available. However, it is key to ensure they can access ancillary services markets to reach broad adoption – as proven in NESO’s Quick Reserve auction. System services markets, like inertia or voltage control markets, are being rolled out in multiple countries, including the UK, Germany, the Netherlands.

Coinciding with the heatwaves, the Polish Transmission System Operator – PSE, has proposed an anti-blackout recommendations package on July 2. The package proposes several measures, such as: access to real-time data from distributed energy sources and storage units, and an ability to control their operations in emergency situations; wider adoption of dynamic tariffs; or increased participation of generation units in the balancing market. All of these measures should provide the TSO with more control over the grid, and eliminate the risk of blackouts ahead of time.