Across India, millions of people are making ... calculations. The share of Indians with air conditioning is still small, roughly 5 percent, but it’s growing fast.Rising incomes are making air conditioners more attainable, while rising temperatures are making them a necessity. “There are hundreds of millions of people for whom air conditioning doesn't seem like a luxury good,” said Michael Greenstone, director of the Energy Policy Institute at the University of Chicago. “It can mean the difference between life and death.” 

The cooling industry has found a ready market in Ahmedabad, the largest city in the state of Gujarat. The city bakes each summer until the monsoon comes, at which point temperatures drop into the 90s and the humidity rises to stifling levels. Above the city’s winding streets, crowded with fleets of auto rickshaws and mopeds, billboards declare that every home deserves Hitachi cooling. Elsewhere, Panasonic ads extol the speed at which its “life conditioners” can cool a room. Apartment ads list AC first among amenities offered, and restaurants promise relief from the heat. Appliance shops along the roadside display the industry’s major players in big letters on their windows: Hitachi, Mitsubishi, Blue Star, Panasonic, General — the King of Cool, etched in glass with a crown — Daikin, Carrier. 

The world is on track to add 700 million new ACs by 2030, and 1.6 billion by 2050, largely in hot, developing countries like India and Indonesia. But the AC boom threatens to worsen the crisis it’s responding to, and widen the divide between those who can afford to stay cool and those left out in the heat. 


In late July, on the leafy campus of Ahmedabad’s CEPT University, Professor Rajan Rawal stood outside his lab, drinking chai with his students, sheltering from a monsoon rain that was flooding the city. Tall, with short gray hair and dark mustache, he speaks with patrician weariness about the folly of the world of cooling. 

Refrigerated cooling first caught on as a way to preserve food, then to control humidity in factories. Finally it was used to cool people, but, Rawal said, it’s a blunt instrument, and shouldn’t be the only one. “You can’t simply take one pill and cure everything, or just take a fighter jet and win a war. You need various kinds of weapons and various medicines, in same way you need various strategies for buildings.” 

Some examples lay strewn about his lab: a segment of brick wall on a wheeled rack, meant to study heat absorption; a model building surrounded by lights on arcing tracks, meant to observe shade as the sun’s position changes; in the basement, a climate-controlled chamber where students sometimes sit to test the effectiveness of various cooling technologies. 

The proliferation of air conditioning enabled building designs that were wholly dependent on air conditioning. Age-old cooling tricks like courtyards, crossbreeze-promoting corners, eaves, porches, and other architectural features were dispensed with. Developers, eager to capitalize on cheap designs and interior floor space that would’ve been stiflingly hot previously, turned to solid office blocks, glass towers, and boxy, mass-produced tract homes, relying on air conditioning to make them habitable. Air conditioning, writes Gail Cooper in Air-Conditioning America, “was the modern building’s iron lung.” 

As India urbanizes, the CEPT team sees an opportunity to take a different path when it comes to cooling, one with a smaller role for the air conditioner. “Do we go the route of the US and Western countries, not worry about efficiency, just whatever provides the cooling?” Yash Shukla, another researcher in Rawal’s program, asked me. “The climate impact of that is significant. If we can find a better approach to have the same level of comfort, why not do it the better way?”

Their research took them somewhere esoteric: thermal comfort standards. When figuring out what sort of HVAC equipment to put in a building, engineers use models that attempt to predict what temperature and humidity levels occupants will be happy with. It’s a necessarily difficult attempt to quantify something subjective. One of the widest-used thermal comfort standards, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 55, acknowledges thermal comfort is “a condition of mind” before setting out on a valiant effort to model everything from the metabolic rate of someone typing to the insulation factor of calf-length socks.

ASHRAE dictates a comfortable temperature in the range of 67 to 82 degrees, depending on the season and other variables, yet it’s become a widely acknowledged problem that air-conditioned buildings are too cold. Figuring out exactly why — whether the standard is resulting in overpowered AC systems, building managers are overcooling so men can wear suits in summer, or some other reason — is “the holy grail,” in the words of one researcher, and the subject of ongoing research. 

There are big gains to be had in raising building temperatures. In 2005, Japan launched an energy-saving initiative called Cool Biz, setting office thermostats at 82 and encouraging workers to forgo ties and heavy business suits. After the 2011 nuclear meltdown, the program became Super Cool Biz: jackets came off, and polos, even aloha shirts were encouraged. If you needed sartorial guidance, Uniqlo published recommendations, and the Environment Ministry sponsored a fashion show where men demonstrated how to pull off a blazer with shorts. By 2010, the latest year for which data is available, Japan estimated that the program cut as much CO2 as almost 4 million households would emit in a month. 

The CEPT researchers felt India’s standards needed revising, too. Most of the international comfort standards were developed by institutions in the global north, based largely on surveys of people unaccustomed to India’s heat. “The premise was that occupants in buildings in India are very different from occupants in Europe or the US, which is where the international standards come from,” said Sanyogita Manu, who led the study. “We didn’t have a thermal comfort model of our own.” 

Manu traveled to office buildings from humid Chennai in southern India to mountainous Shimla in the Himalayan foothills, wielding monitors to test the temperature, humidity, and airspeed, and asking workers whether they were comfortable. 

She found that Indians are indeed comfortable at slightly higher temperatures than existing models would predict, particularly when in buildings that aren’t sealed up and air conditioned. Previous research has shown that in buildings without AC, people are comfortable at higher indoor temperatures the hotter it is outside; they don’t expect refrigerated coolness, they wear lighter clothes, they open windows, they use fans, and their bodies adjust to the heat. The mere feeling of control over things like windows and fans also makes people feel more comfortable, even if the temperature remains the same. The models that reflect this are called “adaptive,” but they’re typically only used for buildings that aren’t air conditioned at all. The CEPT team found that the same phenomenon also applied to mixed-mode buildings — buildings that switch on the AC when it gets hot — and that people were comfortable in environments up to almost 88 degrees. Last year, the Indian government adopted their model in the national building code. It’s expected to reduce energy spent to cool a building by a third.