In stifling apartments and sweaty row houses in England, Germany, and even Scandinavia, some Europeans are considering a very American idea: They really need an air conditioner.One of their most accessible options, though, might feel unfamiliar to anyone accustomed to central air. Among Europe’s commonly used types of air conditioning is a clunky, inefficient unit that stands a few feet high and has a wide exhaust tube meant to go out a window. Such units are typically “a panic-buy on a hot weekend,” Brian Motherway, the head of energy efficiency at the International Energy Agency, told me. People grab the first machine they see and end up living with it for a decade, he said. Many people leave the window gap around the exhaust tube uncovered, letting hot air right back in. Walking down a Paris street last week, I saw three different stores where such units stood beside a door propped open by the tube.Sales of air conditioners of all sorts are climbing in Britain too. I’ve lived in London for 25 years, and I don’t recall ever hearing anyone talk about buying a home air conditioner—until three acquaintances mentioned, unprompted, on the same sweltering day, that they had purchased one, or were considering it.Much of Europe wasn’t built for air-conditioning, or for coping with hot weather at all. In Britain, for instance, which has been long accustomed to cool summers and dark, rainy winters, older houses like mine are poorly insulated and often leave inhabitants baking when outside temperatures climb. But many newer buildings are designed to retain heat and maximize sunlight, making them also poorly suited for the new normal, Andy Love, a sustainability consultant who founded Shade the UK, an advocacy group that presses for smarter building regulations, told me. However sleek and modern the big glass apartment towers going up around London look, he said that many residents are “moving into those flats in the winter to then find out in the summer, it’s a furnace.” Britain’s Climate Change Committee, which advises the government, put the problem bluntly in a report in May: “The UK was built for a climate that no longer exists.”All across the continent, Europeans enduring heat waves that are growing more frequent and intense are coming to similar realizations about their own buildings and cities. The zinc roofs that top nearly four-fifths of Parisian apartment buildings, for instance, create baking conditions for those beneath. Temperatures are brutal, too, in the concrete towers on the city’s poorer outskirts, where high electricity prices make some people wary even of running fans. France’s housing minister, Vincent Jeanbrun, said that one in three dwellings in the country was “like a thermal kettle.” Many European nations have worked hard to improve buildings’ energy efficiency, but although insulation can help modulate temperatures in summer as well as winter, many homes have also been made airtight to retain heat.Now Europeans urgently need ways to cool down. Although climate change will cause the biggest absolute increases in heat in African nations, eight of the 10 countries likely to see the most “dramatic relative increases in the number of days that require cooling” are in northwestern Europe, a study by researchers from the University of Oxford and the University of Bristol found. That list includes Switzerland, Britain, and Norway, and all of those places, the study warns, are unprepared.Already this summer, two major heat waves have broiled Europe. During the first, Ireland, France, and the United Kingdom sweated through their hottest-ever May temperatures. A month later, France notched its two hottest days and its hottest night since records began: Thermometers soared past 110 degrees Fahrenheit in the west and 104 degrees in Paris. Spain reported its two hottest June days since at least 1950, and Britain, where temperatures reached 99 degrees, recorded its three hottest June days. The temperature in Basel, Switzerland, hit 100 degrees. Germany and Austria are enduring heat in the 90s, and braced for worse as the weather moves east. Temperatures this high can be life-threatening: More than 200,000 people have died because of heat in Europe in just the past four years, the World Health Organization estimates.The imperative of reducing that toll prompted Britain’s Climate Change Committee to warn that although installing shades, awnings, and shutters can and should help lower temperatures, air-conditioning and other cooling systems will be needed in many homes, hospitals, long-term-care facilities, and schools. That need couldn’t have been clearer this week, as patients sweltered and radiation and MRI machines broke down in hospitals just as emergency rooms were swamped with heat-stricken arrivals.Making changes like those the committee recommends will take money—potentially $10 billion annually between now and 2050—and time. A 2021 report estimated that less than 5 percent of U.K. homes had air-conditioning, although one market survey reported more recently that the number with an AC had doubled in the past three years. Even so, air-conditioning the country will take decades. The climate panel recommended that temperatures be kept to safe levels in all hospitals by 2035, in long-term-care facilities by 2040, and in schools and prisons by 2050.The shift to AC is happening across Europe, where only about 20 percent of homes currently have air-conditioning. (Compare that with about 90 percent in the United States.) Ownership is skewed toward the south of Europe—about half of homes in Italy and 40 percent in Spain use it, for example. But a survey in Germany found that AC ownership jumped by 6 percent between 2023 and 2024. Even residents of Scandinavia and the Baltic countries are buying air conditioners, Simon Pezzutto, who studies cooling demand at the Institute for Renewable Energy at Eurac Research, in Northern Italy, told me.Those clunky portable units do ease discomfort, at least; another widely available air-conditioning option, known as a split unit, is typically more efficient, but also more expensive and harder to install. Reversible air-to-air heat pumps, which are gaining popularity, are an even more efficient option and can both heat homes in winter and cool them in summer.In Europe, where electricity prices are significantly higher than in the United States and incomes are typically lower, the price of cooling can mean a painful surprise when the power bill comes. If air-conditioning use spikes rapidly, it could also burden a grid that is not yet ready for big new peaks. In a taste of that possible future, tens of thousands of French homes lost power during this week’s brutal heat. Electricity prices spiked as demand climbed, and some nuclear reactors had to curtail generation. Britain’s grid operator coughed up an estimated $13 million to get extra generation online.Roxana Slavcheva, a buildings expert at the World Resources Institute, told me that the continent would benefit from making sure that the air conditioners it does use are as efficient as possible. But it also needs to prioritize less energy-hungry cooling measures, including better ventilation and more shade for both streets and buildings, she said. In southern Europe, Italy’s wooden shutters and the Greek islands’ thick white walls moderate temperatures, Anna Mavrogianni, a built-environment professor at University College London, told me. Street trees, pergolas, and parks can make being outside more enjoyable, and even help reduce the urban heat-island effect, which makes cities hotter than surrounding areas. Awnings stop heat before it gets inside, as does orienting new homes to minimize direct sunlight on big windows. Light-colored or reflective paint keeps temperatures down, and ceiling fans help too.Such upgrades aren’t all easy—or quick. In Paris, for instance, officials sometimes decline permission to modify those hot zinc roofs because they’re part of the city’s distinctive look. Elsewhere, too, local planning rules aimed at preserving historic buildings’ aesthetics can mire exterior changes in red tape. In Britain, windows that typically open out instead of in mean that external shutters can’t be installed. Love, the sustainability consultant, knows that retrofitting millions of homes and thousands of neighborhoods is a daunting project that will take years, if it happens at all. Done right, the changes he envisions could make Britain “feel a little bit more Mediterranean than we’re currently used to,” he said. But with the heat here today, “people now just want solutions.”