I was visiting Jaipur a few years ago to attend the farewell celebration of a distant relative. It was April and as you'd expect, hot & dry. I jotted something in my pocket notebook as one afternoon as we were in our air-conditioned Uber ride to a famous kachori place. Across the crossing, I noticed, a tempo driver had wedged the cooler against the open back window of the vehicle, and water sloshed out of the tank onto the floor mat every time he braked.
Late April in Jaipur, around 43 degrees, the kind of dry heat where your lips crack by noon and the steering wheel is too hot to hold. As we were waiting for the shopkeeper to handover the kachoris, and the driver had stopped for filling his water bottle, I interacted with him for about a minute. I couldn't anymore - it was too hot! He had bought it that morning from a shop in Johari Bazaar. Forty litres, a single plastic grille, a fan, I'm sure, you could hear from the next room. I kept thinking what I think every time I see one of these machines doing its job in a place like this: the expensive option would have been the wrong one.
In about half of this country, on the days that matter, the cooler is the correct machine and the AC is the overbuilt one. There is nothing sentimental in that claim. It rests on physics, on the electricity bill, and on the grid the machine has to live on.
Start with what is actually happening inside that leaking box.
A desert cooler is a fan, a tank of water, a small pump, and three sides of wet pad. The pad is wood wool, or on better units a honeycomb of cellulose, and the pump keeps it soaked. The fan pulls hot dry outside air through the wet pad, and as the air passes through it picks up water. To turn that water from liquid into vapour, the air has to give up energy. Roughly 2,260 kilojoules for every kilogram that evaporates, and the energy comes out of the air itself as a drop in temperature. It's why you feel cold stepping out of a pool on a windy day, and why a wet earthen pot keeps water cool in a village kitchen.
That is the whole machine. No gas, no compressor. It doesn't 'make' cold; it collects the temperature drop from evaporating water and blows the result at you. All you need is water. On a Jaipur afternoon a forty-litre unit will drink two or three litres an hour, sometimes more when the air is bone dry. That's the only running cost of a few buckets of water a day, refilled by hand, in a part of the country where water is not something you take for granted either.
The lowest temperature a cooler can ever reach is the wet-bulb temperature of the incoming air, the reading you'd get from a thermometer wrapped in wet cloth and waved around. Evaporation alone cannot take air below it. In dry Jaipur air the dry-bulb might read 43 and the wet-bulb might sit near 24. That gap of nineteen degrees is the cooler's entire working range.
The gap matters because air can only hold so much water before it's full. Hot air holds a lot, cool air very little. When outside air is hot and dry it's nowhere near full, so it has enormous room to take on vapour, and every gram costs it heat. The drier the incoming air, the more water it swallows and the harder it falls on the way through the pad.
Now imagine taking the same machine to Chennai in August. Dry-bulb 35, wet-bulb already 29. The range of temperature has collapsed to six degrees, and almost all of it is unusable because the air arriving at the pad is already close to full. All the cooler does is turn a warm room into a clammy one, adding moisture to air, making it more humid which no one wants. Someone in Chennai who tells you coolers are useless isn't wrong.
So the cooler isn't a worse air conditioner. Below a certain humidity it works; above it, it doesn't. The line runs roughly through the middle of the country, and a very large number of Indians live on the dry side of it. Delhi, Jaipur, Nagpur, Lucknow, Ahmedabad, much of the Gangetic plain and the whole north-west through the worst of the pre-monsoon heat. That is the demographic centre of the country in exactly the weeks the heat is trying to kill people. The coast and the deep south get their relief from the AC, and good for them. Everyone between Punjab and Vidarbha gets it from a fan blowing through a wet pad, and the calendar that matters runs April to June, before the rains arrive.
Now the part that decides it: what the two machines actually cost.
A 1.5-ton air conditioner pulls between 1,000 and 2,000 watts while the compressor runs, and the compressor is the whole point of an AC. A desert cooler runs a fan and a pump, which together draw 150 to 300 watts. Call it a tenth. In units of electricity the AC burns 1.2 to 1.8 an hour and the cooler sips 0.1 to 0.3. Run the cooler eight hours a day for a month and you've spent around 300 to 500 rupees. Run the AC the same hours and you're looking at two to four thousand, and on an old three-star unit closer to the top of that. For a household where the summer electricity bill is a real decision, that gap is the difference between cooling the room and not.
You'd experience similar things at the shop as well. A solid forty-litre cooler in that Johari Bazaar shop would come for about five to eighteen thousand rupees. The 1.5-ton split the salesman would rather sell starts around thirty and climbs past sixty, before installation, before the copper piping, before the stabiliser you'll need because the voltage is unreliable anyway. One machine costs a tenth to buy and a tenth to run. It's no surprise that for a family on the dry side of the line, the price tag made the decision.
Then there's the power grid where these machines go. The voltage sags in the afternoon when everyone's compressor kicks in at once, and the supply cuts out for an hour at a time. An AC compressor shouldn't ideally receive these spikes. They burn out and restart frequently and every restart slams the motor against a system still under pressure, and a few summers of that does what you'd expect. A fan and a pump on the other hand don't care. They stutter, they stop, they start again when the light comes back, and they keep doing it for ten summers. There is nothing precious inside a cooler to protect.
Ok one important thing. The cooler needs an open window for air to come in. An AC wants the room sealed, because it's chilling the same air over and over and any leak is wasted work. A cooler is the opposite. It adds moisture constantly, and if you trap that moisture in a closed room, within an hour the room saturates, the evaporation stops, and you're sitting inside a warm humidifier. So you leave a window open at the far end, and the cooler pushes a steady current of cooled outside air through the room and out the other side. The room never holds the same air twice. On a dry night that's genuinely better to breathe than the same AC lungful cycled twenty times with the doors shut. Nobody who buys a cooler thinks of this as a feature. It's just how the thing works.
Which brings me to the man who understood all of this before the market did. In 1988, when a cooler at home was still something of a luxury, an architect from Ahmedabad named Achal Bakeri borrowed seven lakh rupees from his father and started making them. He had a diploma in architecture from CEPT. He figured that the ugly metal box in everyone's house could be a designed object with plastic instead of rusting steel and in a shape you wouldn't want to hide. The company was Symphony. It nearly went bankrupt in the years he tried to diversify into washing machines, water heaters and, of all things, air conditioners, none of which the market wanted from him. The share price fell to almost nothing in the early 2000s. So he went back to the one machine that fit the country he was selling into.
Today Symphony has shipped past twenty-seven million coolers, leads the organised Indian market with something like a fifth to a quarter of it, and sells into sixty-odd countries from Ahmedabad. The Indian cooler market around it was worth about 117 billion rupees in 2024 and is climbing past 200 billion.
I make hardware, and I keep that story close because the builder's pull always runs the other way. More sensors. A compressor instead of a pump. An app. A spec sheet that wins the customer over during a comparison debate at a Croma store. The crude product feels like a confession that you couldn't build the good one for modern homes. Correct. But, the driver in the Tempo had worked out the difference without a word of technology or smartness. He bought the cooler because, for 43 dry degrees and a bill he actually had to pay, it was the machine that fit. The AC would have been the more impressive thing in the room, and the wrong thing in the room.
The map of India, the wallet and the power grid decide the machine, and none of them care which product has the better engineering. A builder who forgets that keeps shipping the advanced version into a place that needed the cheap one, and then calls the customer unsophisticated for choosing correctly.