Europe is sweltering in record-breaking temperatures this week, and across the continent people are largely trying to cope without air conditioning.

Less than 10% of households in Europe have an AC unit at home. But as temperatures rise, that figure is set to climb. Rising AC use may present new challenges, as most systems used today are still inefficient and produce emissions that drive climate change. In extreme cases, when adoption gets high enough, too many units working overtime can overload the electrical grid on hot days.

Climate change is making extreme heat the norm across more of the world, increasing the need for adaptation. But in the case of AC, some experts are concerned about how to balance that need with the harms the solutions can cause.

Global AC sales more than tripled between 1990 and 2016, according to a 2018 report from the International Energy Agency. That growth is likely to continue, with energy use for cooling worldwide expected to triple again between now and 2050.

A large fraction of increasing AC adoption globally is focused in hot countries like India and Indonesia. By 2050, about half the growth in AC cooling capacity will be from just two countries, India and China, according to the IEA. In these countries, incomes are rising, giving people access to AC for the first time, says Enrica De Cian, an environmental economics researcher at Ca’ Foscari University in Venice, Italy.

But AC adoption is also rising in relatively richer countries, including across Europe, largely due to urbanization and climate change pushing temperatures higher, De Cian says.

Many Europeans are still hesitant to welcome ACs with open arms. “Seeing ACs as a solution to heat waves and to climate change is of course a bit problematic because of the energy that’s being used,” says Daniel Osberghaus, an energy and climate economics researcher at the Leibniz Centre for European Economic Research in Germany.

Today, cooling devices like ACs make up about 10% of global electricity consumption — and since most of the world’s electricity still comes from fossil fuels, that’s a significant chunk of worldwide emissions. Because of their massive energy use, “they do get a bad reputation,” says Kevin Lane, an energy analyst at the IEA.

Cooling units can particularly challenge the electricity grid because they all tend to switch on around the same time, during the hottest parts of the day. This problem is evident in places like Texas, where summers are hot and AC use is widespread. Texas grid operators frequently urge people to turn down their ACs during peak hours in the afternoon to avoid blackouts.

More efficient alternatives to the window units common in cities today do exist, Lane says. Split units, or heat pumps, can act as both cooling and heating devices and may be more efficient than current AC technology. Upfront costs for heat pumps are still relatively high, though lifetime costs can rival other options because of energy savings.

And for places with relatively moderate climates where heat waves are short, passive cooling options like reflective roofs, shaded windows, and better-ventilated buildings can lessen the need for costly active cooling like ACs, Lane adds.

But realistically, for more of the world, cooling is becoming a necessity rather than a luxury. For these places, Lane says, “the question is how we make it affordable, how we make sure the environmental impacts are reduced.”

One of the most effective ways for governments to push more climate-friendly cooling is to set regulations that outline minimum efficiencies for new units, Lane says. Rebate programs can also help people afford more efficient but expensive options.

AC is somewhere between a luxury and a necessity today, depending on the circumstances. And while many people could use their AC units less often and set them to higher temperatures, cooling is becoming a requirement for a growing swath of the globe.

“With the growing prevalence of these really extreme heat waves, one of the key impacts of air conditioning is that it can insulate you from some of these really dangerous health impacts,” says Stephen Jarvis, a researcher at the London School of Economics. “In those circumstances, it really is becoming more of a necessity.”