Fans, Air Coolers and Air Conditioners: What Actually Cools a Room
They sit next to each other in the same aisle and are marketed with the same word — cooling. Only one of them lowers the temperature of a room.
Every summer the same three products get compared as if they were competing versions of one appliance. They are not. They do different things, and the disappointment people report usually comes from buying the wrong category rather than a bad model.
Fans move air. They do not cool it.
A fan does not change the temperature of a room — strictly speaking it adds a little heat, because the motor is not perfectly efficient. What it changes is you. Moving air speeds up the evaporation of sweat and strips away the thin layer of warm air sitting against your skin, which can feel like a drop of several degrees.
That makes a fan excellent value where it works, and useless where it does not. It works when you are in the airflow. It does nothing for an empty room, and it does very little once the air itself is above skin temperature and already humid.
Best for: desks, bedsides, kitchens, circulating cooler night air. Costs: typically 20–75 W — pennies a night.
Evaporative coolers trade humidity for temperature
An evaporative cooler (sometimes sold as an "air cooler" or "swamp cooler") draws air through a wet pad. Evaporating water absorbs heat, so the air that comes out really is a few degrees cooler than the air that went in — usually in the region of 3–7 °C in favourable conditions.
The catch is in the word "evaporative". The drier the air, the better it works. In a dry continental or desert climate it can be genuinely effective. In a humid coastal summer the air is already close to saturation, very little water evaporates, and you get a fan that also makes the room muggy. Evaporative coolers also need ventilation — a cracked window — which is the opposite of what you do with an air conditioner.
Rule of thumb: if your weather app regularly shows humidity above about 60%, an evaporative cooler will underperform badly. Check a week of local humidity readings before buying one.
Air conditioners are the only ones that remove heat from the room
An air conditioner uses a refrigeration cycle to move heat from inside to outside. That is why it needs a hose, a window unit or an outdoor condenser — the heat has to go somewhere. It is also the reason air conditioning dehumidifies: water condenses on the cold coil and drains away.
This is the only one of the three that will bring a closed room down to a set temperature and keep it there. It is also the most expensive to buy, the loudest, and by far the biggest consumer of electricity — typically 700 W to 1.4 kW for a portable model, against 50 W for a fan.
Choosing between them
- You need to sleep and the nights are mild: a decent fan, plus airing the room out after sunset, is often enough.
- Dry climate, moderate heat, tight budget: an evaporative cooler is worth considering — with a window open.
- Humid climate, or you need a reliable set temperature: only an air conditioner will do it. Anything else will disappoint.
- You cannot vent a hose anywhere: you cannot use an air conditioner. Any product claiming to cool a room with no exhaust at all is describing an evaporative cooler, whatever it is called on the box.
Free things that help more than people expect
Before spending anything: close blinds and curtains on the sunny side during the day, and open the building up once the outdoor temperature drops below the indoor one. External shading beats internal shading, because it stops the heat before it comes through the glass. Turning off unused electronics removes a surprising amount of load in a small room. None of this replaces air conditioning in a real heatwave, but it changes how hard the appliance has to work — and how much it costs to run.