Nearly 90 percent of homes in the United States have air conditioning, and in Europe, where summers are now warming twice as fast as the rest of the world, that number is closer to 20 percent

We will state the situation plainly and let it speak for itself.

According to the US Energy Information Administration, approximately 90 per cent of American households have air conditioning. According to the International Energy Agency, around 20 per cent of European households have it. According to the World Health Organisation, the WHO European Region — which spans 53 member states, a wider area than the EU — is warming at roughly twice the global average rate, and heat claims more than 175,000 lives annually across that region. Research published in The Lancet found that in 2019 alone, 195,000 heat-related deaths among people over 65 were averted because of AC adoption. 

The region that most needs cooling infrastructure has the least of it. The region with the most of it built the majority of that infrastructure during decades when its summers were mild enough that a few warm weeks per year were treated as an occasional bonus rather than a public health variable.

How the gap formed

Air conditioning penetration in the United States was driven by a combination of factors that did not apply in Europe at the same time. Post-war suburban expansion in the American South and Southwest put large numbers of people into climates where summer heat was not an occasional inconvenience but a persistent, months-long physiological challenge. The technology arrived and spread because the need was immediate and the infrastructure of cheap electricity and car-centric housing made installation straightforward.

Northern and Western Europe’s summers, until recently, did not present the same conditions. Average July temperatures in Paris, London, Amsterdam, and Berlin were historically mild enough that the absence of air conditioning was not a significant hardship for most of the year. Buildings in these cities were designed for insulation against cold winters rather than heat dissipation in hot summers: thick walls, small windows relative to southern European architecture, limited cross-ventilation in the denser urban housing stock. The buildings retain heat. The air conditioning to counteract this was never installed because, for most of the twentieth century, there was not much heat to counteract.

This is no longer reliably true. The 2003 European heatwave produced an estimated 70,000 excess deaths across the continent. The 2019 and 2022 heatwaves set successive temperature records in France, Germany, the United Kingdom, and the Netherlands. This June, forty people drowned in France seeking relief from extreme heat, Spain recorded temperatures above 45 degrees Celsius, and the United Kingdom endured its hottest June on record. Heatwaves of this severity are now, according to climate researchers, roughly thirty times more likely to occur than in the pre-climate-change era.

The thermodynamic irony of the situation

The argument against widespread residential air conditioning in Europe has historically come in several forms. The electricity grid constraints are real: a rapid expansion of AC adoption would place significant demand on grids already under pressure from the energy transition. Energy costs in Europe run higher than in the United States, partly owing to the lack of domestic natural gas supplies in many European nations. The environmental argument follows directly: a 2022 analysis estimated that air conditioning accounts for four per cent of global greenhouse gas emissions, roughly double that of the aviation industry. Cooling a building during a heatwave contributes, in a small and indirect way, to the conditions that caused the heatwave.

This is a genuine tension, not a trivial one. The IEA has published scenarios in which rapid growth in global air conditioning demand outpaces the deployment of clean electricity, producing a net increase in emissions that warms the planet faster. The air conditioning paradox is real: the more widely it is adopted in response to heat, the more it contributes to the heat that drives adoption.

The counterargument is equally real. European heat mortality is heavily concentrated among elderly people without access to cooling. The 2003 event’s death toll skewed heavily toward people over 75 living alone in apartments without air conditioning, during a stretch of nights that did not cool below 25 degrees Celsius. At that temperature, sleep is disrupted and core body temperature cannot recover. The accumulation of heat stress over multiple nights is what drove the mortality, not a single extreme afternoon.

What the gap looks like going forward

The gap is already closing, unevenly. Italy’s experience is instructive: in the summer of 2003, an estimated 10 to 15 per cent of Italian households had air conditioning. By 2024, according to Italy’s National Institute of Statistics, that figure had reached 56 per cent. Italy now accounts for one-third of all electricity used on air conditioning across the European Union. In the United Kingdom, approximately four million homes now have air conditioning, twice as many as three years ago. In France, during this June’s heatwave, shops ran out of units. Germany’s uptake remains around 18 per cent, close to the continental average; northern and economically poorer countries sit lower still.

The European building stock is not going to be retrofitted rapidly. The electrical grid is not going to be decarbonised overnight. The summers are not going to stop warming. These three facts are proceeding simultaneously, at different rates, in a context where the policy response to each interacts with the others in ways that are difficult to optimise. Experts advising on the transition argue that the key is solar-powered, energy-efficient units rather than the grid-straining adoption of conventional AC, though uptake of that model has been slow.

The US situation is not simply better by virtue of high AC penetration. American air conditioning consumption is a significant portion of national electricity demand; the equipment is unevenly distributed by income; and the buildings in which poor Americans experience heatwaves are often older, with less efficient units, less insulation, and electricity costs that make sustained operation during peak periods a genuine financial burden. The 90 per cent penetration figure obscures considerable variation in what “having air conditioning” actually means in practice during a week of extreme heat.

Still: the gap is 90 versus 20, in a context where European summers are warming twice as fast as the global mean. The conditions that made the gap tolerable for most of the twentieth century are no longer present. The gap persists.