Air conditioning: the benefits, problems and alternatives

Amid record-breaking heat, increased access to air conditioning could save lives – but AC units are damaging the environment. Are there other options?

Much of the Earth sweltered under record-topping temperatures this month. Phoenix, Arizona, broke its record for most 110F (43.3C) days. California’s Death Valley had its highest temperature ever. An airport in coastal Iran saw a heat index of 152F, while Beijing saw a record stretch of 95F days.

Oppressive heatwaves have become more frequent and more severe as a result of the climate crisis – a trend that’s expected to continue, and could worsen in proportion to how quickly we can transition from fossil fuels.

To beat the heat, people are increasingly turning to air conditioning. The number of AC units globally could increase by 244% by 2050, according to the International Energy Agency, and demand could rise by 59% within the US, according to a 2020 analysis by independent research group Climate Central.

Increased access to air conditioning could save lives; after all, in the US, extreme heat is the single deadliest form of extreme weather. But it could also come with drawbacks.

Below we look at the challenges today and in the years ahead, and consider some of the alternatives.

The technology can be expensive to purchase and run, often rendering it inaccessible to poor communities in the US and globally. In the US, research shows lower-income households are much more likely to lack access to the technologies. And one 2019 study found that between 1.8 and 4.1 billion people in developing countries who regularly experience dangerously high temperatures lack access to cooling technology.

“In much of the world, in many countries, we’re concerned that people who most need air conditioning don’t have it,” said said Narasimha Rao, a professor of energy systems at Yale University who co-authored the paper.

AC usage also puts pressure on electricity grids. That can be risky: if a five-day heat wave and a power outage hit the city of Phoenix at the same time, more than 50% of the city’s current population of 1.4 million could end up in the emergency room, one recent study found.

Many are working to make air conditioners more affordable and to improve the reliability of electricity grids. Yet there is another problem: air conditioners warm the Earth.

The appliances use a lot of energy. Between now and 2050, cooling technologies including AC units are projected to be the biggest contributor to growing energy demand, according to the Intergovernmental Energy Agency – a problem, since most global energy currently comes from fossil fuels. The US broke its summer record for daily gas consumption on at least two separate occasions, data from S&P Global Commodity Insights shows, and AC usage is a key contributor.

Most AC models also require the use of planet-heating chemicals to cool the air. The most commonly used refrigerants in ACs are hydrofluorocarbons (HFCs) are potent greenhouse gases – thousands of times more effective at trapping heat than carbon dioxide.

Some air conditioners do use the more climate-friendly refrigerants hydrofluoroolefins (HFOs), though these can still create ecological damage. Other alternatives include ammonia and propane, but both can be harmful to humans when they leak.

Companies are now also using newer kinds of refrigerants, like R-32, which is an HFC that is half as planet-warming as older ones traditionally used for air conditioning.

And experts say that by employing other strategies to lower temperatures in homes, we can lessen the environmental toll of air conditioning, allowing people to stay cool without warming the planet.

One of the buzziest air conditioning technologies are electric heat pumps, which can both heat and cool homes. On hot days, the appliances pump hot air out of the home and draw cool air in.

Traditional ACs and heat pumps both cool homes by directly lowering air temperature and also by pulling moisture out of the air, which can make a home more comfortable. But combining the two processes makes the appliances “terribly inefficient”, said Les Norford, professor of building technology in the Department of Architecture at MIT.

Norford and others are working to develop new technologies that separate the two functions to boost efficiency. Some models use living membranes or physical desiccants – materials that suck up humidity – instead of energy-powered processes to pull moisture from the air.

Improving the energy efficiency of air conditioners is crucial. According to the International Energy Agency, in 2018, the average air was less than half as efficient as the best available technology. And the least efficient models – often found in low-income households – require even more power to run, rendering them both more climate-warming and expensive.

Other common technologies can play a major role in cooling homes. Fans, for instance, are much cheaper and far less energy consuming than ACs, said Rao, the Yale professor. They can also be surprisingly effective, especially in hot, dry environments.

“In some cases they can provide up to 2C of relief,” he said.

Rao is also studying the potential for dehumidifiers to be used as a widespread cooling technology, as they can also greatly improve comfort in hot and muggy areas.

“In Mumbai, where I’m from, you can have tremendous relief from drying the air,” he said. “In my house it’s pretty hot and humid, but I go to the basement which has no air conditioning, just dehumidification, and it’s still so much cooler.”

In hot and dry heat, another useful low-energy technology is the air cooler, also known as the swamp cooler. These devices use a fan to recirculate air across a cool, wet material and then disperse the freshly dampened, cool air into the home. Like dehumidifiers and fans, swamp coolers are cost and energy efficient, and are also widely available.

Buildings can be better designed to keep temperatures down.

One crucial strategy is weatherization, said Vivek Shandas, a geography professor at Portland State University who studies the impacts of climate change in urban areas.

“We’re often throwing AC at homes – especially older homes, homes where lower-income communities of color live – without doing any weatherization like insulating or sealing up the cracks the windows and the doors where that outside extreme heat can come in,” he said. As a result, residents can end up being forced to crank the ACs to their highest settings to keep indoor temperatures down.

Weatherization, said Shandas, would reduce the amount of AC required to maintain a comfortable setting, resulting in lower energy bills and greenhouse gas emissions.

Some homes are also built with highly heat-absorbing materials. Residents of mobile homes and trailers, which are often made with steel or aluminum, are often most vulnerable to extreme heat, said Shandas.

In south Asia and other parts of the global south, said Rao, metal roofs – often found on slums – are common because they are inexpensive.

“An aluminum sheet for a roof is the worst thing you can do from a heat perspective,” he said.

But some materials used to make homes, such as brick and stone, can absorb and release heat more slowly. Improving the availability and affordability of such materials could save lives in the extreme heat.

Homes – especially roofs – can also be painted white to lower indoor temperatures. White roofs products stay coolest under the sun’s rays because they reflecting away between 60 and 90% of sunlight, according to the Department of Energy. And buildings can be designed with ventilation in mind to lower temperatures. Wind towers, for instance, can be built to draw cool breeze indoors; placing ponds of water underneath them can make the structures even more effective.

Shade can make a big difference within the home and outside of it. The simple act of drawing opaque curtains closed, for instance, can help push down indoor temperatures, said Shandas. Communities can employ that same strategy by planting trees throughout neighborhoods.

“We know that treed neighborhoods can be up to 15 degrees cooler than ones with no trees,” said Shandas.

Trees and other plant life can also be installed on rooftops to help insulate buildings from hot air outside. These strategies are especially useful in urban “heat islands” where abundant concrete draws in thermal energy – areas which are disproportionately occupied by low-income people of color, Shandas added.

Experts say a world eliminating AC would be dangerous.

“There are some parts of the world where really, you cannot do without air conditioning, where you have really muggy weather throughout the year,” said Rao.

But strategically using other methods to cool down communities could cut costs and emissions. It could also cut down on a knock-on effect of air conditioning: in highly dense areas, running them can raise outdoor temperatures by 1C (1.8F).

Different strategies will work best in different contexts, said Shandas. And in some cases, several should be applied at once.

“We are not in a position as a species to necessarily think that we are going to be able to find that silver bullet out of this extreme heat,” said Shandas. “We need to be finding the myriad different effective solutions that are socially and politically palatable, and that are sustainable in the long run.”