Beyond the Thermostat: The Surprising Science and Strategy Behind India’s 24°C AC Revolution 

India’s mandate to set air conditioner defaults to 24°C is a strategic policy born from necessity, blending compromise with science to address a growing energy crisis. With AC sales soaring and cooling consuming 25-30% of peak electricity demand, this “magic number” represents a calculated effort to reduce grid strain and advance India’s Net Zero goals. While scientifically rooted in “thermal comfort”—a concept combining temperature and humidity—the 24°C standard is also a practical compromise, chosen for being both energy-efficient (saving 4-5% more power per degree) and publicly acceptable.

Critics note that humidity drastically affects perceived comfort and that past studies have a North Indian bias, making a single national standard imperfect. However, the policy also aims to correct wasteful consumer behavior, like overcooling spaces, and is part of a larger strategy that includes better building design and efficient technology to ensure responsible and accessible cooling for all.

Beyond the Thermostat: The Surprising Science and Strategy Behind India’s 24°C AC Revolution 

As the Indian summer sun beats down, pushing temperatures into the high 40s, a quiet revolution is taking place inside millions of homes and offices. It’s not just about staying cool; it’s about redefining what “cool” actually means. At the heart of this shift is a seemingly simple number: 24°C. 

This isn’t an arbitrary decree. It’s a calculated strategy born from a urgent national challenge. In 2024, a record 14 million air conditioners were sold in India. By 2030, that figure is projected to more than double. This explosive growth isn’t just a sign of rising incomes; it’s a looming crisis for the nation’s power grid. Cooling already accounts for a staggering 25-30% of India’s peak electricity demand, and that share is set to skyrocket. 

In response, the Bureau of Energy Efficiency (BEE) has championed a mandate: all new, star-rated ACs must have a default thermostat setting of 24°C. This “magic number” is more than a suggestion—it’s a critical piece of India’s puzzle to achieve energy security, cut carbon emissions, and fulfill its ambitious Net Zero mission. 

But why this specific temperature? Is there real science behind it, or is it just a political compromise? The answer, it turns out, is a fascinating blend of both. 

The Art of the Possible: A Policy Forged in Compromise 

When the BEE first introduced the 24°C default in 2020, the public reaction was a mix of skepticism and mockery. In a nation where summer heatwaves can be lethal, the idea of a government-mandated temperature felt to many like a “One Nation, One Temperature” gimmick, utterly disconnected from the reality of citizens battling 50°C heat. 

However, according to insiders, 24°C was chosen not as an ideal scientific absolute, but as a “technically viable and politically acceptable” consensus. 

“We would have pushed our heels in and said 26°C, but 24°C was something everyone could agree on,” revealed Ajay Mathur, a former director general at the BEE. 

The calculus was based on energy savings data from manufacturers. They demonstrated that energy consumption doesn’t increase linearly as the temperature drops: 

• At very low set-points (18-22°C), each degree lower consumes roughly 6% more energy. 

• In the mid-range (24-26°C), the savings per degree are around 4-5%. 

• At 27°C and above, it’s about 3%. 

By anchoring the default at 24°C, the BEE targeted the “sweet spot”—a temperature that delivers significant energy savings (5-6% per degree warmer) without triggering widespread consumer rejection. It was the art of the possible. 

The Science of Comfort: It’s Not Just the Heat, It’s the Humidity 

The theoretical foundation for 24°C lies in the study of **”thermal comfort”**—defined as “the condition of mind which expresses satisfaction with the surrounding thermal environment.” But this is where the simple number meets complex human biology. 

Experts are quick to point out that focusing solely on temperature is a mistake. 

“People often say ‘temperature’ as a proxy. Actually, temperature and humidity both play a very important role in your thermal comfort,” explains Satish Kumar, CEO of the Alliance for an Energy Efficient Economy (AEEE). 

This is the critical caveat often missed in the public debate. An AC’s job isn’t just to cool the air; it’s also to dehumidify it. In high-humidity regions like Kolkata or coastal Kerala, the air can feel oppressive even at lower temperatures because sweat doesn’t evaporate effectively. Here, an AC must work much harder, running its compressor longer to wring moisture from the air, which drastically increases energy use. 

In such conditions, a setting of 24°C might be necessary to achieve a feeling of comfort equivalent to a drier 26°C. Conversely, in the dry heat of Rajasthan, a higher temperature might feel perfectly comfortable. This highlights a major gap in the data: many Indian thermal comfort studies have a “North Indian bias,” underscoring the need for more localized research. 

Professor Rajan Rawal of CEPT University, whose team developed the India Model for Adaptive Comfort (IMAC), emphasizes that true comfort depends on four factors: air temperature, humidity, air velocity, and radiant temperature. His research confirms that comfort is relative to outdoor conditions. 

“In Jaisalmer, you might want 30-31°C indoors, while in Ladakh, 20°C indoors would be comfortable. Human comfort is linked to outdoor temperatures—the higher the outdoors, the higher the indoors we accept, and vice versa,” says Rawal. 

This makes a single national number a blunt instrument. However, as Rawal concedes, policy requires simplicity. A default of 24°C provides a strong, energy-efficient baseline from which individuals can adjust based on their local climate and personal needs. 

Breaking Bad Habits: Why We Crank the AC Too Low 

Beyond science and policy lies a major hurdle: human behavior. B. Thiagarajan, Managing Director of Blue Star, identifies a common problem. 

“Often, installers leave ACs at 18-19°C after testing, and users never change it. Others believe that setting a lower temperature will cool the room faster, which is a complete misconception,” he notes. 

This leads to a culture of overcooling. Cinemas, malls, hotels, and offices often blast ACs, creating Arctic environments that force patrons to use jackets or blankets indoors—a profound waste of energy and a symbol of irresponsible consumption. 

The 24°C default acts as a gentle nudge, a “reset” for this ingrained behavior. It establishes a new normal, encouraging users to first see if 24°C is comfortable before automatically reaching for a lower, more wasteful setting. 

The Stakes: Cooling, Climate, and a Net Zero Future 

The push for 24°C is far more than a energy conservation measure; it’s a frontline strategy in the fight against climate change. The numbers are staggering: 

• India’s peak energy demand is around 240-250 Gigawatts (GW), with cooling taking up 60-75 GW of that. 

• By 2030, driven by AC sales and the urban heat island effect, cooling demand could surge to nearly 100 GW. 

• Every kilowatt-hour of electricity saved on cooling directly reduces CO₂ emissions, given that India’s grid still emits about 727 grams of CO₂ per kWh. 

The India Cooling Action Plan (ICAP) aims to reduce cooling demand by 20-25% by 2037-38. Widespread adoption of the 24°C setting could save an estimated 20 billion units of electricity annually, preventing 16-18 million tonnes of CO₂ emissions. 

But experts agree that thermostat settings are just one piece of the puzzle. The future of sustainable cooling lies in a triad of solutions: 

• Passive Cooling: Better building design, green roofs, cool paints, and traditional architectural wisdom like cross-ventilation to reduce the need for mechanical cooling altogether. 

• Efficient Technology: Transitioning to the most energy-efficient ACs and exploring alternative cooling technologies. 

• Responsible Consumption: The cultural shift—using ACs wisely, not wastefully. 

For Professor Rajan Rawal, the ultimate goal is balance. “Access to cooling is a must for health and productivity, but consumption has to be responsible… The solutions are always somewhere in the middle, not at the extremes.” 

The message from policymakers and scientists is clear: in the quest for comfort, cool no longer has to mean cold. By embracing the 24°C standard, India isn’t just adjusting its thermostats; it’s taking a critical step toward a more sustainable and resilient future.