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The short version
An air cooler and an air conditioner look like they do the same job, but they work in very different ways. Sales pages often blur this, so here is the plain difference.
| Air cooler | Air conditioner | |
|---|---|---|
| How it works | Evaporates water into the air | Moves heat from inside to outside |
| Effect on humidity | Adds moisture | Removes moisture |
| Best weather | Dry heat | Any, including humid heat |
| Cools a whole room? | Not really | Yes, if sized correctly |
| Needs to vent outside? | Needs an open window | Yes, through an outdoor unit or the back of a window AC |
| Running cost | Low | Higher |
| Water to refill | Yes | No |
| Upfront cost | Lower | Higher |
How an air cooler works
Evaporating water takes heat out of the air. You feel this when you step out of a bath into a breeze. An air cooler does the same thing with a tank of water, wet pads and a fan. You feel cool air near it, but the heat stays in the room and the air gets damper.
In dry heat, that can feel great. In a humid room, the air already holds a lot of water, so less evaporates and you get less cooling. The air can start to feel sticky.
How an air conditioner works
An air conditioner uses a refrigerant to pull heat from the room and push it outside. That is why a split AC has an outdoor unit, and a window AC sits in an opening with its back end outside. It also dries the air, which is a big part of why it feels comfortable.
Which part of India are you in?
Your weather matters more than any feature on the box.
| Where you live | Cooler | AC |
|---|---|---|
| Dry summers: much of Rajasthan, Delhi, Haryana, inland Gujarat, Madhya Pradesh and Vidarbha | Works well from April to June | Works all summer |
| Same areas during the monsoon | Weak, because the air turns humid | Still works |
| Humid coast: Mumbai, Chennai, Kolkata, Kochi, Visakhapatnam | Weak for most of the year | The better choice |
| Mild cities and hill towns | Rarely needed for long | Often not needed, try a fan first |
Many homes in north India use both. A cooler handles the dry weeks of May and June, and the AC takes over when the monsoon brings sticky nights.
Room size and AC tonnage
A cooler is sold by tank size and airflow. An AC is sold by tons, which is a measure of cooling power, not weight. Use this table as a rough starting point only.
| Room size | Rough AC size |
|---|---|
| Up to about 120 sq ft | 1 ton |
| About 120 to 180 sq ft | 1.5 ton |
| Above about 180 sq ft | 2 ton |
Go a size up for a top floor room, a west facing room or a room with large windows. A room with a hot roof above it has much more heat to remove.
What each one costs to run
This table is an example, not a promise. It uses ₹8 per unit, 8 hours a day and a 30 day month. The watts are also example figures. An AC does not draw full power all the time, so we have used an average. Your own rate depends on your state and how much you use, so check your bill.
| Example | Watts | Units a day | Cost a day | Cost a month |
|---|---|---|---|---|
| Ceiling fan | 75 | 0.6 | ₹4.80 | ₹144 |
| Air cooler | 150 | 1.2 | ₹9.60 | ₹288 |
| 1.5 ton AC, average draw | 1,000 | 8 | ₹64 | ₹1,920 |
Many electricity boards charge more per unit as your use rises. So a summer of AC use can cost more than this sum shows. Check the BEE star label on an AC, and set a sensible temperature instead of the lowest one.
Living with each one
A cooler needs a window open a little, so that damp air can leave. It needs refilling, and more often in the hottest weeks. Hard water leaves scale on the pads, so clean them and the tank through the season. Empty the tank when it is not in use, because mosquitoes can breed in standing water.
An AC needs a fixed place, professional installation and yearly servicing before summer. If you rent, ask your landlord first and check where the outdoor unit can go. If you have voltage swings, check whether you need a stabiliser. Ask what installation includes, because pipes and stands can cost extra.
Which should you buy?
Choose an air cooler if you live somewhere with dry heat, you only need cool air near one person, you cannot fit an air conditioner, or you want something to carry between rooms.
Choose an air conditioner if you live somewhere humid, you want to cool a whole room, or heat is a health risk for someone in your home.
Try a fan first if you only need a little relief. A fan is cheap and moves air across your skin.
A word on safety
During a heatwave, older people, babies and people with health conditions can be at real risk. Do not rely on a small cooler to keep someone safe. If your home gets dangerously hot, follow local health advice and go somewhere with proper cooling.
Claims to be careful with
Be careful with any small cooler that promises to replace your air conditioning or cut your bills by a large amount. A small tank and fan cannot do the same job as a machine that moves heat outdoors. Check the details and the return policy, then decide with realistic hopes.
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Common questions
Is an air cooler the same as an air conditioner?
No. An air cooler evaporates water to cool the air close by. An air conditioner moves heat out of the room and removes moisture.
Do air coolers work in humid weather?
Not very well. They rely on evaporation, which slows down when the air is already humid.
Can a small air cooler replace air conditioning?
Generally no. It can give one person some relief, but it does not move heat out of the room.
Should I keep a window open when using an air cooler?
Yes. A cooler needs fresh, dry air coming in and damp air going out. In a closed room the air gets humid and the cooling fades. An AC is the opposite, and works best with windows and doors shut.
Can I run an air cooler on a home inverter?
Often yes, because a cooler draws far less power than an AC. Check the watts on the cooler against the capacity of your inverter. Most home inverters are not meant to run an AC.