Severe summer heat waves are undermining energy security throughout Europe. The continent is enduring a blistering, parched summer that is driving air conditioning demand to unprecedented levels at the very moment that rivers are warming and receding — with devastating consequences for both the nuclear power sector and hydropower reserves.

Last month, France was forced to curtail output and shutter nuclear reactors at a record pace due to insufficient supplies of cooling water. This week, Hungary took the extraordinary step of shutting down the Paks nuclear power plant over the weekend, abruptly cutting off approximately 40 percent of the country's electricity generation. "Due to the further drop in the Danube's water level," Prime Minister Péter Magyar tweeted on Saturday, "tomorrow it will be completely shut down for the first time in 44 years."

The Paks shutdown triggered a massive swing in regional electricity prices, with costs soaring to €500 per megawatt-hour — a level that dwarfs typical European wholesale prices, which generally trade well below €100 per megawatt-hour under normal conditions. Hungary's challenges are far from over — the coming week will be a critical period as temperatures climb to dangerous levels. "An energy crisis situation may arise from Monday," Magyar warned. "Coordinated steps and self-restraint will be needed to avoid more severe consequences."

The crisis comes at a delicate moment for European energy policy. Nuclear power supplies roughly a quarter of the European Union's electricity and has been central to the bloc's decarbonization strategy, with several member states reversing earlier phaseout plans or advancing new reactor projects to meet net-zero targets and reduce dependence on imported fossil fuels. Yet the events of this summer expose a structural vulnerability: the low-carbon technologies most relied upon for steady, round-the-clock power are themselves acutely exposed to the climatic shifts they are meant to help mitigate.

The timing is especially dire given that access to air conditioning can be a matter of survival for vulnerable and elderly populations. According to a study published in The Lancet00005-7/fulltext), nearly half a million people worldwide died from heat-related causes each year between 2000 and 2019, the majority of them elderly and thus more susceptible to extreme temperatures. Air conditioning currently prevents approximately 190,000 heat-related deaths annually.

Conditions could deteriorate further. It is only early August, and historically Europe's key waterways, including the Danube, reach their lowest levels toward the end of the month or in September. Meanwhile, the effects of climate change continue to intensify. Europe — the world's fastest-warming continent — must prepare for extreme heat and water stress becoming routine.

"We have to plan our power system so that this might be our new reality," Zsuzsanna Pató, power system lead for Europe at the non-profit Regulatory Assistance Project, told Bloomberg. "We don't usually have such hot spells, but we just have to get used to it."

The situation presents a double-edged sword: the clean energy technologies most needed for round-the-clock power — nuclear and hydropower — are precisely the ones becoming hardest to maintain and expand under these conditions. "As it gets hotter, things stop working quite so well," Iain Staffell, associate professor of sustainable energy at Imperial College London, told DW. "I think we do need to adapt the power system to cope with the changing weather."

Nuclear power is considerably more water-intensive than many other energy sources, consuming far more water per kilowatt than renewables such as solar and wind. These requirements are impeding the sector's growth in water-stressed regions and generating significant political friction in countries like Australia, where water is a precious commodity.

However, according to the Breakthrough Institute, "nuclear reactors don't need to be so thirsty." Expanding nuclear power in a changing climate will require stricter guidelines for water recycling at nuclear facilities. Reactor design is also evolving rapidly as the sector grows more competitive and privatized. Future reactors may rely on gas rather than steam, while others will employ air cooling or molten salt models — both of which require substantially less water.

By Haley Zaremba for Oilprice.com