TLDR: The temperature you set on your AC remote is only one variable in what makes a room comfortable. Humidity, solar load, building orientation, and time of day matter just as much. After a year of sensor data in Navi Mumbai, I stopped picking a fixed number and started reading conditions instead, then automated the whole thing with IR blasters.
Ask anyone in India what they set their AC to and they'll answer immediately. 24. 25. 22 if they run cold. It's one of those numbers people just know about themselves, like their phone number or their blood group. Everyone has a number.
I had one too. Mine was 25.
I started questioning it after I put temperature and humidity sensors inside my apartment in Navi Mumbai. I was logging indoor conditions every few seconds alongside the AC's power draw, and after a few months the data made something obvious that the number on the remote never could: 25 degrees in March and 25 degrees in August are completely different experiences.
What the sensors showed at the same setpoint
The AC was set to 25. The indoor sensor confirmed 25.2 degrees. And I was uncomfortable. Not dramatically, just that low-grade awareness that the room wasn't quite right. The air felt thick for 25 degrees.
The humidity sensor read 65%. The AC was in cooling mode, not dry mode. It had hit its temperature target and was happy. The moisture in the air was not its problem.
Your body doesn't feel air temperature directly. It feels how fast it can shed heat. When the air is already saturated with moisture, evaporation from your skin barely works. So 25 degrees at 65% humidity is a noticeably different sensation from 25 degrees at 40% humidity.
This was July in Navi Mumbai. Monsoon. The kind of humidity where you step out of a shower and never quite feel dry.
| Humidity | ||||
|---|---|---|---|---|
| Temperature | 30% | 50% | 70% | 90% |
| 22°C | Cool | Cool | Comfortable | Comfortable |
| 24°C | Comfortable | Comfortable | Comfortable | Warm |
| 26°C | Comfortable | Comfortable | Warm | Uncomfortable |
| 28°C | Warm | Warm | Uncomfortable | Uncomfortable |
Look at the 26-degree row. At 30% humidity, it's comfortable. At 90%, it's genuinely unpleasant. Same reading on the AC display. The difference is entirely in what the air is carrying.
What humidity does at 25 degrees
During monsoon in Navi Mumbai, outdoor humidity routinely sits between 80% and 95%. The AC's compressor cycles to hit its temperature target, and it does succeed at that. But cooling air also removes some moisture, and when the incoming humidity is that extreme, the AC is fighting two battles at once. The temperature battle it wins. The humidity battle it often loses, or only partially wins.
The sensor data made this visible. On monsoon evenings with the AC in cooling mode, indoor humidity would settle around 60-65%. The AC had pulled it down from the 85%+ outside, but not far enough. The room was 25 degrees and still felt off. The system was doing everything right by its own metric and still failing by mine.
Switching to dry mode on high-humidity days helped more than lowering the temperature. The goal wasn't a colder room, it was a drier one. That distinction only became clear from the sensor logs.
In dry winter months, the opposite happened. Humidity indoors would drop to 40-50%, and 26 or even 27 degrees felt perfectly fine. The AC was doing less work and the room was more comfortable. The number on the remote was higher but the experience was better.
How the building fights the AC in the afternoon
There's a pattern in my AC's power data that puzzled me at first. On clear days, the compressor would run almost continuously from about noon to 4pm. By 8pm, it would cycle normally, ten minutes on, twenty minutes off. The outdoor temperature difference between 2pm and 8pm was maybe 3-4 degrees. Not enough to explain such a dramatic shift in how hard the AC was working.
The missing variable was solar radiation. At peak sun, the walls, windows, and roof of my apartment absorb heat and radiate it inward. The AC isn't just fighting the outdoor air temperature. It's fighting the thermal mass of the building itself, which has been soaking up energy all morning.
In Navi Mumbai, peak solar elevation hits around 82 degrees in summer. That's nearly overhead. The roof takes the full load. By evening, with the sun below the horizon, that radiant heat input drops to zero. The AC's job gets dramatically easier without the outdoor temperature changing much.
This is something you feel but might not connect to a cause. The room that was never quite cool enough at 3pm becomes perfectly comfortable at 9pm on the same setting. It's not the AC performing better. It's the building no longer fighting against it.
An east-facing bedroom heats up in the morning. A west-facing living room gets hit hardest in the afternoon. The same AC setting performs differently in each room at different times of day, and the reason has nothing to do with the AC.
Three seasons at the same setting
I kept the sensors running through a full year. Same apartment, same AC, same 25-degree setpoint across seasons. The data told three very different stories.
Large indoor-outdoor gap. AC runs long cycles. High solar load adds to the fight. Energy bill peaks.
Temperature gap is smaller but humidity is extreme. AC spends most effort on dehumidification. Can still feel sticky.
Comfortable conditions. AC barely needed most days. Fan mode often sufficient. Running AC here is mostly habit.
The summer data was expected. Large gap between outdoor and indoor temperature, AC working hard, high energy consumption. No surprises there.
The monsoon data was the most instructive. Outdoor temperatures were actually lower than summer, so you'd expect the AC to have an easier time. It didn't. The humidity made every degree of cooling harder to achieve in felt terms. The compressor cycled, the room hit 25 degrees, and I was still uncomfortable because the moisture stayed.
The winter data was the most revealing. The AC was running in conditions where opening a window or turning on a ceiling fan would have been enough. Not because anyone consciously decided they needed active cooling in December, but because the habit of turning the AC on persisted past the conditions that justified it.
BEE's 24 degrees, and what it doesn't say
India's Bureau of Energy Efficiency recommends 24 degrees. It's printed on every AC sold in the country. As a general guideline for reducing energy waste, it makes sense. Plenty of people set their ACs to 18 or 20, which is genuinely colder than necessary and expensive to maintain.
But 24 is not a comfort guarantee. On a dry winter afternoon in Jaisalmer with 25% humidity, 24 degrees might actually feel cold. On a monsoon evening in Navi Mumbai with 90% humidity, 24 might still feel sticky. The recommendation is a reasonable energy policy. It's not a comfort prescription, because comfort depends on variables that a single number cannot capture.
The BEE sticker also doesn't distinguish between a bedroom you cool for eight hours at night and a living room you cool for two hours in the afternoon. The thermal load, the occupancy pattern, the solar exposure, all different. The same number responds to those situations differently.
Homes and offices are different problems
At home, the AC goes on when someone decides it's hot and goes off when they leave or go to sleep. This is how most Indian households operate. The AC runs for a few hours in the afternoon, again in the evening, sometimes through the night in peak summer. It responds to immediate discomfort.
Offices are a different dynamic entirely. The AC system runs on a schedule, often from 9am to 6pm, sometimes longer. In many commercial buildings, the system runs year-round because that's how the BMS is configured. Nobody adjusts the setpoint by season because nobody is tasked with doing so.
This is where the real waste lives. I've been in offices in Navi Mumbai where the AC was running in January. Not because anyone was hot, but because the system was set to cool and nobody told it to stop. People bring jackets to their desks in winter because the office AC is still set to 22. The temperature is technically comfortable. The fact that it's 24 degrees outside and the building is spending electricity to make it 22 inside is the absurdity.
In homes, the waste pattern is different. It's less about running the AC when you don't need it, and more about running it at a setting that doesn't match the conditions. Lowering the number to 22 in monsoon because 25 feels sticky, when the actual issue is humidity, not temperature. Or keeping the same setting year-round without noticing that October and February barely need cooling.
What I actually do now
I stopped treating the AC as a set-and-forget appliance. The sensors made that impossible once I could see the data.
When the humidity sensor reads above 70-75%, I switch to dry mode before I lower the temperature. Getting the moisture out of the air often does more for comfort than dropping a degree. A ceiling fan on low helps move the drier air around the room.
On clear dry days, 26 or 27 is usually enough. Dry heat is more tolerable than people give it credit for, and the energy cost of each additional degree of cooling gets disproportionately expensive as you push the setpoint further from outdoor conditions.
In the afternoon when solar load is high, I accept that the room will be slightly warmer and compensate with airflow rather than pushing the AC harder. By evening, the same setting catches up on its own.
In December and January, I check the outdoor temperature before reaching for the remote. If it's below 26 outside, a fan is usually enough. This sounds obvious written out, but the number of months I ran the AC out of habit before I started tracking conditions is not something I'm proud of.
Eventually I stopped reaching for the remote altogether. The same sensors that taught me what to look for now feed into a system that controls the AC directly. IR blasters pointed at the indoor unit take commands based on indoor humidity, outdoor temperature, time of day, and solar conditions. The system switches between cooling and dry mode, adjusts the setpoint up or down, and turns the AC off entirely when the conditions don't warrant it. It's not a smart thermostat. It's closer to what I was doing manually, just without the forgetting.
The shift wasn't finding the perfect number. It was recognizing there is no perfect number. There's a set of conditions, temperature, humidity, solar load, time of day, what the building has been absorbing, and the right response changes with them. Automating that response was the natural next step once the logic was clear.
The Solar and Climate Intelligence project on this site tracks these variables in real time, solar position, outdoor weather, indoor temperature and humidity, and the relationships between them. It started as a way to understand my own energy bill. It turned into something more interesting.