Europe’s latest heatwave is pushing electricity markets into another period of intense volatility, with France and Germany facing sharp evening price increases as demand for cooling rises and power generation weakens.
Electricity costs in both countries were predicted to shoot up during the peak period in the evening on Tuesday, August 11, as there will be a drop in solar power while air conditioners continue to consume energy. Electricity costs were stated to be above €170 per megawatt hour from 8 p.m. until 10 p.m. in both France and Germany compared to below €20 per megawatt hour in both places at about 1 p.m. Day-ahead market had an equally notable increase. The electricity cost increased by 20.5% in France to around €141/MWh, according to LSEG figures reported by Reuters.
The corresponding price in Germany was quoted at 22.8% higher at €138.50/MWh, while a separate assessment put the French cost at €142.50/MWh. The varying numbers depend on the nature of the European electricity market. While day-ahead prices refer to electricity expected to be used the next day, intraday prices keep fluctuating depending on the predictions made regarding the demand, wind, solar generation and availability of plants.
The immediate concern is not that France or Germany has completely run out of electricity. Rather, the heatwave is reducing the amount of inexpensive and reliable generation available at the precise moment when demand is increasing. That imbalance is sending wholesale prices sharply higher.
Nuclear output faces climate pressure
France is particularly exposed because its electricity system depends heavily on nuclear power. The country’s nuclear fleet normally provides a large and relatively stable supply of electricity, allowing France to export power to neighboring markets. But many reactors use rivers for cooling, making their output vulnerable to high water temperatures and low river flows.
During the latest heatwave, water temperatures in rivers including the Rhône, Garonne, Seine, Meuse and Moselle reached levels that forced EDF to restrict production or temporarily shut down reactors. The restrictions are intended to prevent the discharge of excessively warm water from damaging river ecosystems.
EDF has stressed that the measures are environmental and regulatory precautions rather than evidence of an immediate reactor-safety problem. The company said
“the impact of the measures on electricity production is negligible,”
while officials and market analysts emphasized that the effect can nevertheless become substantial during a few high-demand hours.
This is crucial in the understanding of how markets react to the problem. Though the loss of several gigawatts is a small fraction of the total amount of nuclear energy produced in France each year, the effect on price can be significant if the system is already tight. According to Reuters, in July, the EDF had cut generation by 6.3 GW in 8 reactors due to persistent heat and warm water in rivers. During the peak of the general heat wave, the limitation reached up to 8-9 GW of the French nuclear power capacity, or roughly one fifth of its usual capacity during summers.
Carbon Brief noted that three of the 57 reactors in France were shut off during the heatwave in July, while there was also some restriction of generation in another 7 reactors. Overall, this led to almost 9% decrease in French nuclear generation. The phenomenon is not new. In 2003, the exceptionally hot summer witnessed reduction of French nuclear capacity by over 6 GW. However, such events happening again in 2026 raise the question about reliability of power systems designed for historical climate conditions.
Germany’s wind and solar problem
Germany’s pressure is different but closely connected. Its electricity system has a much larger dependence on weather-sensitive renewable generation, particularly wind and solar power. During the current heatwave, weak wind speeds are expected to reduce wind generation, while solar output declines rapidly during the evening.
Solar generation can provide abundant electricity during the middle of the day. That helps explain why prices in France and Germany were reported below €20/MWh around 1 p.m. But as the sun sets, photovoltaic output drops while households and businesses continue to use air-conditioning. The market must then replace solar power quickly with gas, coal, imports, storage or demand reduction.
This daily transition is known as the evening solar ramp. When wind generation is also weak and French nuclear availability is restricted, the ramp becomes more expensive and more difficult to manage.
Gas-fired plants can respond more flexibly than nuclear stations, but extreme heat reduces their efficiency. Rystad Energy estimated that output from a typical gas plant may fall by approximately 7% to 12% on a 30°C day because hot air reduces turbine efficiency.
The same weather conditions can therefore increase demand while weakening several sources of supply at the same time. Cooling systems consume more power; gas turbines work less efficiently; wind speeds may fall; and solar generation disappears after sunset.
France’s export role is weakening
The impact of decreased production from France’s nuclear power plants also extends to other neighboring countries. France usually ranks among Europe’s largest producers of electricity, but with a well-functioning network of nuclear power plants. In the recent June heatwave, it was noted that France only exported about 3 GW of electricity, which is down from the 10–12 GW that was recorded the previous week. It is worth noting that electricity markets within Europe are highly interrelated and connected with each other.
Countries such as Germany, Belgium, Britain, Switzerland, Italy and many others use cross-border electricity flows in order to deal with the shortage of energy supply. When France has an excess of nuclear power, it exports electricity relatively cheaply. If this power is restricted, the countries will have to find ways to procure power from more costly gas-fired plants. Simultaneous heatwaves exacerbate the problem since it becomes harder to produce an excess of power in the region. Grid operator RTE says that France’s electricity production capabilities will suffice to satisfy the needs of the country during heatwaves.
This means the country’s physical supply position remains manageable. But a secure grid and affordable electricity are not the same thing. The system may retain enough capacity while prices rise sharply because the marginal units needed to meet the evening peak are expensive.
Earlier price spikes show the risk
The current August price surge follows several more extreme episodes earlier in the summer.
Germany’s day-ahead electricity price reached €210/MWh on June 23, according to LSEG data cited by Reuters. During one June evening, German prices reportedly rose from approximately €86/MWh at midday to €566/MWh at 8 p.m.
Other markets recorded even higher short-term prices. Belgium exceeded €1,038/MWh, the Netherlands reached about €902.47/MWh and Denmark’s western bidding zone approached €786.83/MWh during the same period.
Intraday prices on June 24 were expected to reach around €898.21/MWh in Germany and €639.26/MWh in France. Such prices are generally short-lived, but they reveal how quickly Europe’s power system can move from abundant midday electricity to severe evening scarcity.
The financial effect is already visible. An analysis by 350.org estimated that the June 21–27 heatwave added approximately €371 million to electricity costs in Germany and €360 million in France, or more than €700 million combined in a single week.
These wholesale increases do not automatically translate into the same percentage increase in household bills. Retail customers may be protected by fixed-price contracts, regulated tariffs, subsidies or government intervention. Still, sustained wholesale volatility raises costs for utilities, industrial consumers and households whose contracts are linked to market prices.
Industry and political consequences
The heat wave is bringing to light an increasingly glaring contradiction in Europe’s energy transition. While renewables have delivered electricity extremely cheaply at certain times, mainly because of solar power production, the system does not yet have enough storage and flexibility to transport the cheap electricity into peak hours in the evening. On the other hand, while nuclear is a significant provider of low-carbon baseload electricity, it is vulnerable to heatwaves and drought due to its reliance on river water for cooling purposes. Energy market experts have already predicted that such events could be a frequent source of price instability going forward. The issue is not only about higher average temperatures but also about increased frequency of extremes affecting demand and supply simultaneously. Environmental activists are using the price spike to push for more taxes on windfall profits from the use of fossil fuels.
Andreas Sieber from 350.org said that governments should introduce an ongoing windfall tax on fossil fuel companies and redistribute the money among households, climate adaptation and energy transition efforts. In this regard, the group referred to the EU solidarity contribution after 2022, which yielded around €28 billion in windfall profits from fossil fuels.
The argument has a political dimension. Supporters say fossil-fuel producers benefit when heatwaves push gas-fired power prices higher and should therefore contribute more to protecting consumers. Opponents of broader windfall taxes typically argue that such measures can discourage investment in new energy supply and weaken Europe’s competitiveness.
The crisis is also putting pressure on France’s nuclear strategy. Heat-related interruptions have historically caused only limited losses in annual production, but France’s audit office has warned that climate-related reactor downtime could triple or quadruple by 2050.
The policy choices ahead
The immediate reaction of Europe will be dependent on methods which can provide electricity during short evening shortages. Such methods include battery storage of electricity, pumped hydroelectric storage, better interconnectivity, demand management and increased flexibility of generation. Longer-term actions will have to include design of power plants and power grids under hotter conditions. Nuclear power plant operators will require improved cooling facilities, different water sources or increased usage of air cooling, although all the above actions will face both technical and financial limitations. The process of demand management will become increasingly important. Utility companies can motivate users to use their non-essential electricity consumption in the evenings, and time-based metering and pricing can contribute to lowering simultaneous consumption. Better interconnectivity will allow risks to be shared between countries, although the problem cannot be avoided if heatwave strikes the whole region.
A warning for Europe’s energy system
The France-Germany power price surge is therefore more than a temporary market story. It is a warning that Europe’s electricity system is entering a new climate environment in which summer reliability may become as important as winter reliability.
The current episode combines rising cooling demand, weaker wind, falling evening solar output, reduced French nuclear production and constrained cross-border support. Each factor alone might be manageable. Together, they produce sharp and sometimes extraordinary price spikes.
The central challenge is to preserve reliable electricity without abandoning Europe’s emissions-reduction goals. Gas can provide short-term flexibility but exposes consumers to fuel-price volatility and higher emissions. Nuclear offers low-carbon power but remains vulnerable to hot rivers and drought. Solar and wind are essential for the transition but require storage, transmission and flexible demand.
For now, France and Germany appear capable of maintaining supply. But the market is already showing the cost of operating too close to the edge during extreme heat. Europe’s next energy debate will not be only about how much electricity it can generate. It will increasingly focus on whether that electricity is available in the right place, during the right hour and under the most difficult weather conditions.
