After another punishing European summer, electricity suppliers are being warned that climate change is placing power grids under increasing strain, and at possible risk of collapse.

An international team of researchers have shown how heatwaves impact European countries' ability to generate and supply power, and how they pose an increasing threat to vital national infrastructure.

The researchers from this Department, City University of Hong Kong, and The Chinese University of Hong Kong (Shenzhen), have developed the first open-source toolkit to help national operators understand the different ways that high heat affects their power grid.

"This analysis uncovered hidden structural bottlenecks, and it should be integrated into [power] grid planning and adaptation as heatwaves intensify under climate change."

"This analysis uncovered hidden structural bottlenecks, and it should be integrated into [power] grid planning and adaptation as heatwaves intensify under climate change."

According to the researchers' model simulations, they found that France, Spain and Italy are at highest risk of supply bottlenecks and possible grid failure. Germany and the UK were comparatively more resilient, although the researchers say that the increasing frequency and severity of heatwaves also places their grids at risk of failure.

Preventing power systems collapsing during future heatwaves

"We hope power providers will use these tools to identify vulnerabilities in their systems and can take necessary action to stop them collapsing during future heatwaves," says corresponding author Srinivasan Keshav (right), the Robert Sansom Professor of Computer Science here in the Department.

The study of 'Heatwave-induced capacity bottlenecks in European electricity grids' – which has just been published in Nature Energy – is highly timely. Earth has just experienced its hottest August on record, according to the World Meteorological Organization.

However, the research is not based on the exceptionally hot summer of 2026, but on a long-term study of the heatwaves of 2019, 2022 and 2024. The researchers used these in their exploration of the interlinked ways that heatwaves put strain on electricity grids.

As they explain, heatwaves increase demand for cooling, leading to spikes in electricity consumption. Meanwhile, total power supply falls because, as heat rises, solar panels lose efficiency and both conventional and nuclear output are cut to prevent overheating. The same high-pressure patterns that bring hot weather often also bring low winds, causing wind farms to falter, which further exacerbates the problem.

Power lines, too, must have their load reduced to stop them hitting their heat limits and are additionally at higher risk of breaking as they sag in the heat. When taken together, these connected issues can lead to supply bottlenecks and what is called 'load shedding' – i.e. intentional power cuts to reduce demand and protect power systems.

While these are known problems, the researchers say that conventional models and analyses to date have revealed only parts of the problem and only at a high computational cost. So, they developed their own algorithms to try and capture the full picture of what is going on with a lower computational burden.

Lead author Enming Liang, Research Assistant Professor at City University of Hong Kong, says "Once you combine all the factors together — demand increase, generator capacity decrease, transmission capacity decrease — you can discover hidden bottleneck regions that existing methods can't find. I think that's the most surprising outcome of our simulations."

The researchers applied their model to Western European electricity grids under projected future heatwave scenarios and represented grid configurations. They focused on eight countries (Spain, Portugal, France, Italy, Germany, Belgium, the Netherlands, and the UK) that have all been impacted by recent historical heat waves.

Significant differences in power systems resilience across countries

When they looked at the results produced by their model, they found significant differences across countries. In France, Spain and Italy, they saw that heatwaves would lead to a greater risk of supply bottlenecks and load shedding.

However, it was a different story in Germany and UK where analysis revealed that power systems remained comparatively resilient, although these too showed a rising risk of failure as heatwaves intensify and demand peaks.

The researchers note that their findings assume only a conservative annual increase in demand over the next five years and do not include the emerging boom in datacentre construction. They also assume existing storage capacity is fully charged when a heatwave arrives, which may not always be the case.

Existing power storage resources won't prevent power cuts

"Even under that ideal assumption, existing storage resources are still insufficient to prevent load shedding," says corresponding author Minghua Chen, Presidential Chair Professor at The Chinese University of Hong Kong (Shenzhen) and Professor at City University of Hong Kong. "I think that's a genuinely alarming, surprising finding from this research."

The researchers make several recommendations to help operators heat-proof their grids. These include building energy storage capacity near high demand locations, upgrading existing transmission lines to carry more power at higher temperatures, and even applying a cooling, reflective coating to powerlines.

They also considered whether countries could look to their neighbours for back-up power during a heatwave but found that while it works in some cases, it's not always a reliable strategy.

"Cross-border support is not a uniform remedy for heatwave-induced bottlenecks," they concluded in their paper. "Its value depends on whether neighbouring systems have surplus capacity under [the same] heat stress and whether [there is] available surplus capacity in neighbouring systems, and sufficient transmission infrastructure to deliver power where needed."

Downloadable HEAT-Analysis toolkit

The researchers are making their data sets, algorithms and source code available as a downloadable toolkit called HEAT-Analysis that they hope will "provide actionable insights for near-term resilience planning and investment decisions". Operators simply plug in proprietary data about their country's infrastructure, and the tool reveals vulnerabilities and lets them test different solutions.

"I'd say it represents a paradigm shift for European grid operators," says Prof Chen. "They should really be using heatwave or summer-peak conditions in their planning and stress-testing, alongside traditional winter peaking. I hope our work is raising people's attention to that."

They caution that there are inevitable limitations on their work, such as uncertainties about climate and demand projections, and the limited resolution of publicly available grid data.

But they say that even with these limitations, their tool "identifies where, to what extent, and through which coupled physical mechanisms, heatwaves create operational stress under the represented grid infrastructure."

They add that "this analysis uncovered hidden structural bottlenecks, and it should be integrated into [power] grid planning and adaptation as heatwaves intensify under climate change."