This is not a warning about the current situation, but the result of a model based on a scenario in which the entire continent switches to renewable energy sources. According to scientists, the necessary backup capacity would be very expensive.
The summer of 2026 raised previously unforeseen questions about the future of Europe’s energy sector. Repeated heatwaves reduced river flows or warmed river water to such an extent that nuclear power plants in a number of countries were unable to cool their reactors adequately and had to reduce output. Hungary was affected most severely, losing most of the generating capacity of the Paks power plant on the Danube and therefore a large share of its electricity supply. Some power plants cooled with seawater also had to reduce output because jellyfish, which multiply more rapidly in warmer water, clogged their systems.
Hungary is to shut down the Paks nuclear power station completely due to low water levels in the Danube (in Czech)
In addition, demand for electricity rose significantly, particularly in the evenings, because of unbearably hot tropical nights. Together, these factors placed excessive strain on the continent’s power grid. It was not the first time that Europe’s energy system had suffered from an unusual combination of meteorological and climatic conditions. At the end of 2024, for example, low levels of sunshine coincided with insufficient wind, causing sharp fluctuations in electricity prices and increasing dependence on fossil fuels and imports.
What path, then, should Europe’s energy sector take? Experts from a wide range of fields are examining this question, and researchers from the Technical University of Denmark (DTU) and Newcastle University have now contributed to the debate. They developed a model of a future zero-emission European energy system and tested it using 80 years of historical meteorological data to determine how it would cope with periods of low wind and solar power generation combined with high demand.
A nuclear power station in France has shut down three reactors. Because of jellyfish (in Czech)
Based on these historical data, they concluded that a fully zero-emission European energy system would face the greatest risk in winter, during prolonged cold spells lasting several days and accompanied by little or no wind. This scenario is particularly challenging because such periods cannot be bridged using electricity stored in batteries alone.
“Future energy systems will rely heavily on renewable sources because they offer the cheapest way of generating electricity and strengthen our energy independence. However, backup capacity is needed to cover energy shortfalls when demand exceeds supply,” said Marta Victoria of DTU, one of the study’s authors. “We also found that the capacity required to keep the system secure during such periods is rarely used at other times. It is more expensive than renewables or other technologies, such as hydropower, making it difficult to finance under current market conditions and resulting in high electricity prices.”
To conduct the analysis, the researchers used an energy-system model to construct a counterfactual scenario showing what a zero-emission energy system would look like. They assumed the climate conditions of the present-day world but made all energy sources sustainable—put simply, they removed all fossil-fuel sources. Using historical meteorological data from 1941 to 2021 enabled them to capture both typical conditions and more extreme years that could affect future energy systems.
Experts refer to the critical periods that pose the greatest threat to Europe’s energy system as “energy droughts”. These are periods in which both wind and solar power generation decline simultaneously. Because Europe’s electricity grid is highly interconnected, such events can affect large parts of the continent at the same time.
For example, in 2021, unusually low wind speeds across north-western and central Europe reduced wind power generation for several months, contributing to higher electricity prices. Several years earlier, in January 2017, a cold spell combined low wind power generation with high demand for heating, placing additional strain on the electricity systems of several countries.
A study claims that climate change is having a major impact on this year’s drought in Europe (in Czech)
“Our approach identifies when the system is under the greatest pressure, what causes these situations and how the system responds to them. The greatest risk occurs during the dark winter months, when low wind speeds coincide with low temperatures. From the perspective of the energy system, extreme weather therefore does not necessarily mean ‘bad weather’,” said Aleksander Grochowicz, a postdoctoral researcher at DTU and the study’s lead author.
The study also distinguishes between short-term and long-term resilience challenges. Short-term resilience refers to the system’s ability to cope with events lasting hours or days, such as a sudden drop in renewable energy generation. Long-term resilience concerns the overall design of the system, including how much generation and storage capacity should be built to withstand fluctuations over years or decades.
“We have shown that backup energy capacity improves short-term resilience, while long-term resilience depends on the system being adequately sized and having a sufficient share of renewable energy sources,” Grochowicz said.
A key finding is that energy supply depends on many factors, including the mix of renewable sources, other low-carbon sources, batteries and other storage facilities, as well as the transmission grid. Backup capacity is needed to manage short-term pressures. However, Europe’s energy systems are not yet sufficient to cover prolonged shortfalls.
Billions are being channelled into battery storage. Network capacity is holding back its development (in Czech)
According to the authors, renewable energy systems are extremely complex, which is both good and bad news for continent-wide grids. This complexity makes them very difficult to model. At the same time, however, it is also an advantage, as it enables the system to cope with extreme situations—provided there is effective coordination and planning. The problem lies not so much in energy generation itself as in the economics: the financial viability of backup capacity is highly uncertain. Extreme weather events are so rare and unpredictable that backup systems may be used for only a fraction of the time, making it extremely difficult for investors to recoup the cost of building them.
“The expansion of renewable energy must be accelerated, as it offers the best strategy for securing cheap and reliable electricity for almost the entire year, reducing emissions and strengthening energy security,” Victoria added. “We need to think more carefully about resilience during short periods when renewable sources are insufficient, and about how much we are willing to pay for it. Better planning encourages investment and improves energy security, making the costs worthwhile. We identified when the system comes under the greatest strain and how often this occurs, providing a clearer basis for planning a resilient energy system.”
Link to the study (in English)
An article written by Tomáš Karlík (CT), initially published on 24 August 2026, 11:56 (CEST)