Air conditioning: Can people stay cool without warming the planet?

As heat waves sweep across the Northern Hemisphere this summer, there is increasing attention on what many experts have long warned will be a catch-22 of climate change: As temperatures climb and hot spells last longer, billions more people will need or want air conditioning – and because of expanding economic development, a growing number will be able to afford it.

But air conditioning and electric fans already account for about a fifth of the electricity used in buildings across the world, according to the International Energy Agency. And recent estimates from the National Renewable Energy Laboratory, part of the U.S. Department of Energy, say air conditioning globally is responsible for around 4% of the world’s greenhouse gas emissions.

In other words, as climate change warms the Earth, the demand for cooling increases. But more air conditioning means more warming. 

This has become the focus of a growing movement of engineers, entrepreneurs, policymakers, and academics who are trying to balance the need for cooling with the necessity of reducing greenhouse gas emissions. 

It is a balance, many say, that will require everything from behavioral changes to new efficiency requirements to improved technology.  

“The demand for air conditioning is going up very, very steeply,” says Rachel Kyte, dean of The Fletcher School at Tufts University. “But we’ve got the opportunity to take a vicious cycle and turn it into a virtuous cycle.”

Air conditioning and electricity

The heart of the air conditioning paradox is both in how the devices work and what is happening to the climate.  

Essentially, air conditioners take heat from inside a house, or room, and then move that heat outside. They generally do so using chemical refrigerants, which, if leaked into the atmosphere, can have a global warming effect some 2,000 times more potent than carbon dioxide. That’s the first climate issue.

Secondly, it takes a lot of air conditioning to make the system work. When the temperature is higher inside, the air conditioner has to work exponentially harder to suck the heat out. And when it’s hotter outside, it takes even more effort to force that inside air into the external environment.

A recent study from the nonpartisan research organization Pecan Street, for instance, found that when temperatures in Texas went from 97 degrees in May this year to a high of 109 degrees in July, the 12-degree temperature differential led to a 48% increase in electricity demand between 2 p.m. and 8 p.m.

“You have to have a place to put that heat,” explains Scott Hinson, chief technology officer at Pecan Street. 

And there is substantially more heat everywhere. Not only are average global temperatures warming – 2013 through 2021 rank among the 10 warmest years on record – but scientists know that climate change has made far more likely the extreme heat waves that have hit everywhere from Pakistan to Portland.   

Mr. Hinson and other researchers from Pecan Street evaluate electricity usage from homes across the United States where volunteers have agreed to allow circuit-level monitoring. Researchers can collect millions of data points from each home every day, Mr. Hinson says, and one thing is clear.

“What drives the energy use in a house is the HVAC system,” he says.

This wouldn’t have a huge climate impact if electricity grids across the world were all powered by renewable energy. But they’re not. According to the U.S. Environmental Protection Agency, renewables – or those sources that don’t add greenhouse gasses into the air – only contribute about 17% of the country’s utility-scale power. The rest is primarily natural gas, nuclear energy, and coal; in developing countries, where much of the air-conditioner boom is expected to happen, the primary power source is coal. 

Energy efficiency versus price

One clear fix for all of this is to raise efficiency standards on air conditioners, says Iain Campbell, a senior fellow at RMI, a nonpartisan energy think tank that helped run the Global Cooling Prize, an innovation contest for air conditioning. But the way the market works now, he says, is that consumers are far more focused on price than on energy efficiency. And companies, even though they can make far more energy-efficient units, focus on the mass market.

“The manufacturers of air conditioners recognize that people don’t really demand more efficient air conditioning; they demand lower cost air conditioners,” he says. “Much of the innovation within this space has gone into making air conditioners more affordable, … and the industry has done an amazing job of lowering the acquisition cost of this technology. But most of the equipment that we use is less than half as efficient as the best option that’s available on the market.”

Today’s minimum energy performance standards for an air conditioner are about 40% of the best technology available, Mr. Campbell says. If that requirement changed upward, it could save consumers tremendous amounts of money on their utility bills, and also take pressure off electrical grids, which, in recent years, have crashed because of spikes in demand during heat waves. And if manufacturers were required to make more of the higher-efficiency units, their costs would eventually fall as well. 

“We’ve got a problem with the pathway that we are on,” says Mr. Campbell. “But it’s not a know-how deficiency. It’s more of a market failure.” 

Equity through innovation

Vince Romanin, however, sees a market opportunity. He is the CEO of Gradient, a company that uses heat pump technology to make a new sort of window unit that both heats and cools, while using less energy and cleaner refrigerants. Gradient’s purpose, Mr. Romanin says, is both to mitigate climate change and to ensure that marginalized communities have access to economically fair and efficient cooling. In other words, to hit that balanced cycle that Dean Kyte believes is possible. 

“People are going to need AC,” says Mr. Romanin. “It’s a super important tool for protecting those communities against the worst effects of climate change.”  

Gradient’s room-sized units do not require any sort of building retrofit; the units drop over windowsills. This makes them particularly appealing for renters – or for landlords who are willing to make some updates for heating and cooling, but not the sort of expensive, full-building HVAC reconstruction that most high-efficiency, central systems require. This summer, the New York City Housing Authority awarded Gradient a seven-year contract to manufacture 10,000 units for its public housing facilities.

“It’s directly in line with our mission,” Mr. Romanin says. “It focuses on communities that are vulnerable to the effects of climate change and builds a resilient infrastructure … while also pushing the market forward with technology that can help us decarbonize more broadly.”

But it’s not just the air-conditioning technology that can help, experts say. Behavioral changes, such as turning the thermostat up by a few degrees, can save tremendous amounts of energy. This month, Spain prohibited public spaces, such as shopping malls and airports, from cooling below 80 degrees. Italy and Greece are also limiting uses of public air conditioners. 

Shifts in building and community design, whether adding canopy coverage to streets or awnings over windows, can also have a big impact on cooling, says Dean Kyte. There is a balance, she says, between technological innovation, efficiency, planning, behavior – and also a growing awareness of climate change.

“Extreme heat is going to have a really serious effect on the quality of life for many more people,” she says. “I think we’re getting to the point that more people are realizing that being able to stay cool is something that is going to require decision-making.”

Editor’s note: Rachel Kyte’s professional title has been clarified.