New Delhi: Each summer, as India’s peak electricity demand rises, much of the attention turns to a single appliance: the air conditioner. With cooling contributing around 25-30 per cent of the country’s peak energy load, the AC ends up taking much of the blame. In June this year, Union power minister Manohar Lal Khattar proposed guidelines to limit the temperature range for ACs across the country — 20 to 28°C.
This proposal to hardwire a temperature range for new ACs builds upon an earlier mandate by the Bureau of Energy Efficiency (BEE), a statutory body under the Ministry of Power. In 2020, the BEE mandated a default thermostat setting for star-rated air conditioners: 24°C. Now, the ‘magic number’ is back in conversation with a renewed push to discourage consumers from going below this.
The goal, as always, is to save energy, cut emissions, and ease stress on India’s power grid. It also ties directly to the India Cooling Action Plan (ICAP), which seeks to reduce overall cooling demand by 20-25 per cent by 2037-2038.
While it sounds straightforward, the question arises: why 24°C? Is there any science behind it? And will it really make a difference?
The policy compromise
As soon as the announcement was made, a barrage of criticism exploded online. One X user sarcastically asked not to ridicule “the One Nation, One Temperature initiative”. Another called it “a slap in the face of citizens battling 50°C heatwaves.”
Despite criticism, the BEE has stood firm on its recommendation.
“We chose 24°C because it was technically viable and politically acceptable,” said Ajay Mathur, professor in the School of Public Policy at IIT Delhi and a former director general at BEE. “We would have pushed our heels in and said 26°C, but 24°C was something everyone could agree on.”
There was some method to this choice. Manufacturers told BEE that at very low set-points (18-22°C), energy use rises sharply — roughly 6 per cent more per degree lowered. At mid-range (24-26°C), the change in energy use per degree is around 4-5 per cent, and at 27°C and beyond, about 3 per cent. By choosing 24°C, Mathur said, the BEE could meet the energy savings range of 5-6 per cent per degree.
But even this calculation rests on assumptions.
“The oft-quoted 6 per cent [per degree change] is really a range. It’s anywhere between 3 and 6 per cent, and depends on the baseline room temperature and therefore the load conditions,” said Sumedha Malaviya, a researcher who leads building decarbonisation and sustainable cooling work at WRI India.
The science behind comfort
The idea of 24°C as a magic number comes from what experts call “thermal comfort.”
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) defines it as “the condition of mind which expresses satisfaction with the surrounding thermal environment.”
“It’s the temperature at which you will say, ‘I am thermally comfortable’,” said Satish Kumar, CEO of Alliance for an Energy Efficient Economy (AEEE), a Delhi-based non-profit, and a member of ASHRAE. Since comfort differs from person to person, ASHRAE recommends at least 80 per cent of occupants should feel satisfied with the indoor environment.
However, Kumar added that people often say “temperature” as a proxy. “Actually, temperature and humidity both play a very important role in your thermal comfort.”
Crucially, though, most Indian thermal comfort studies don’t account for humidity.
“That’s a major consideration for the 24-degree threshold,” Malaviya said. “Our buildings are not airtight or insulated, and ACs need to be tested in varying humidity conditions.”
But Professor Rajan Rawal of Ahmedabad-based CEPT University, whose team developed the India Model for Adaptive (Thermal) Comfort, said the IMAC indeed considered humidity — specifically relative humidity — along with air temperature, air velocity (wind speed), and the mean radiant temperature of room surfaces.
“Asking someone to maintain four parameters to get thermal comfort is a very impractical policy initiative. So we say operative temperature, which accounts for all four indoor environmental parameters and represents human thermal comfort closely,” said Rawal, a senior advisor at the Center for Advanced Research in Building Science and Energy (CARBSE), CEPT University.
The reason humidity matters is because in humid weather, the AC isn’t just cooling air to the set point, it’s also “working harder to remove moisture,” explained Kumar. That extra effort keeps the compressor running longer, which pushes up electricity use and bills.
In cities with temperatures below 30°C and near 100 per cent relative humidity — for instance, Kolkata in August — the air conditioner may need to be set at about 22-24°C to achieve comfortable humidity.
“When humidity is high, the same 24°C can feel very different than in dry heat,” Kumar said.
That’s not a good sign for India’s varied climate. Unfortunately, though, the data catering to the country’s diversity of cooling requirements shows “a slight bias.”
“A lot of these studies have been done for North Indian climates,” said Malaviya. “There is a need for more research [on] temperature ranges for thermal comfort in the South and eastern parts of the country.”
Rawal agreed that climate and weather at various geographical locations play a decisive role.
“In Jaisalmer, you might want 30-31°C indoors, while in Ladakh or the Northeast, where outdoor temperatures are much lower, 20°C indoors would be comfortable,” he said. “It’s because human comfort is linked to outdoor temperatures — the higher the outdoors, the higher the indoors, and vice versa.”
But such variation, Rawal added, is hard to translate into policy. “Policy can’t say Chennai should do this and another region should do that. It is complicated for adoption, so BEE recommends a minimum threshold and provides an opportunity to modulate the set-point. IMAC also suggests a band of temperatures rather than a single set-point.”
If humidity complicates the science, consumer behaviour does so even more. Many users set the temperature in their ACs far lower than necessary, noted B Thiagarajan, Managing Director of Blue Star. It’s often because installers leave them at 18-19°C after testing, or because people assume the colder the setting, the faster the cooling will be.
“Strictly speaking, the human body even at 26°C should feel comfortable,” Thiagarajan said. “It’s actually the combination of humidity and temperature that matters and not just the temperature alone. But in many places — cinemas, hotels, restaurants and buses — ACs are run unnecessarily at very low temperatures, making people uncomfortable enough to use jackets or blankets indoors.”
Cooling and climate
Ultimately, it’s all about climate change. And everyone, whether consumers, manufacturers or policymakers, will have to act responsibly to reduce emissions as part of the Net Zero mission, Thiagarajan said. In this context, every effort toward cutting emissions assumes significance. That’s why air conditioners are at the heart of this debate, despite only about 8-10 per cent of Indian households owning them.
But demand for ACs is growing exponentially. In 2024, a record 14 million AC units were sold in India. By 2030, this figure will more than double, Thiagarajan said.
“Our projections show that India is the fastest-growing AC market in the world, and by 2050, we will most probably become the largest market,” he added.
This will further push the share of cooling needs in India’s peak energy demand of 240-250 GW. While estimates vary, AEEE’s Kumar puts it around 25-30 per cent (60-75 GW), which could reach close to 100 GW by 2030, driven by rising AC sales and higher urban temperatures from the urban heat island (UHI) effect and climate change.
Given this, researchers are now focused on finding alternative paths to reduce the use of AC itself. One of the ways, Malaviya said, could include better building design — from cross-ventilation to reflective roof coatings and cooling paints.
The emissions link is also direct: India’s grid emits about 727 grams of CO₂ for every kilowatt-hour of electricity generated.
“Whatever energy you save, you can directly link that to carbon dioxide emissions,” Kumar explained. He emphasised moving toward renewables like solar or wind for electricity generation, after reducing cooling demand through measures such as passive building design and the adoption of energy-efficient air-conditioning technology.
The government, meanwhile, is yet to determine exactly how much energy and emissions have been saved since 2020, or how much it expects to save going forward, through the 24°C policy. As per a 2018 estimate by the BEE, setting ACs at 24°C instead of 20°C could save about 20 billion units (kWh) of electricity annually, translating to 16-18 million tonnes of CO₂ if widely adopted.
ThePrint reached out to officials in the BEE with a list of questions for updated figures but has yet to receive a response.
For Rawal, however, the bigger challenge is not just what temperature people set, but how they access and use cooling in daily life.
“Access to cooling is a must for health and productivity, but consumption has to be responsible,” he said. “You don’t have to be a slave to the AC 24/7 throughout the year. During favourable outdoor conditions in the mornings and evenings, we must open windows. The rest of the time, windows can remain shut and airtight. The solutions are always somewhere in the middle, not at the extremes.”
While it remains a challenge to satisfy the cooling needs of a diverse populace, policymakers seem determined to bring Indians on the same page: cool doesn’t have to mean cold.
Note: This article is part of a learning programme organised by the Danida Fellowship Centre (DFC) in Denmark in collaboration with the Royal Danish Embassy in Brazil. ThePrint is participating in the programme ‘Reporting from the Frontline of the Global Climate Crisis in an Era of Fake News’.
(Edited by Ratan Priya)