A cheaper alternative to ACs, the air cooler is efficient for a well-ventilated space. With a few different kinds and sizes. Some are built with wheels in case you want to move them about in the room or to another room. Air coolers work better in dry areas as humidity hinders evaporation and evaporation is part of the cooling process inside these units.
Pros & Cons
Water needs changing
The advantages of an air cooler
The Pakistan summer is quite harsh and lots of people use air coolers to beat the heat. Available in many brands and sizes with some being small enough to fit on a desk for a direct blast. Being a simpler machine it uses less energy and doesn't require installation, this also adds to the fact that it is easier and cheaper to maintain/fix. The overall price is generally also a lot less than any AC, making it a lot more accessible at a larger scale. The fact that is doesn't need gases to cool and doesn't produce much heat while cooling a space makes it a lot more environment-friendly compared to an AC as well.
More efficient ways to use one
A better way to use an air cooler is to have the room ventilated and the air cooler placed by a window. As it uses evaporation caused by warm air passing through the cooling pads, placing it in front of the window helps with that process. One can experiment a bit with how much ventilation is needed in the room to keep the airflow smooth and open the windows the right amount, accordingly. Generally, air coolers work better in dry areas, too much humidity hinders the process of evaporation and thus makes the cooling less efficient. A fair amount of water is used in coolers and needs to be changed often so it doesn't become stale and eventually unhygienic. The temperature settings are also not very precise but make a difference of a few degrees compared to the ambient temperature.
Adding in ice to cool the water
People do add ice to the water, some coolers even have designated compartments for ice but it has to be the correct amount. Too much ice can also hinder the evaporation process and this is also more effective when you are closer to the cooler. The ice cannot affect the overall room temperature and humidity too much.
Some of the known brands manufacturing air coolers include Super Asia, Boss, Geepas, Ditron, Sogo and E-Lite.