The amount of cooling required depends on the area of the room. To calculate the area in square metres:

Room Area BTU = Length (m) x Width (m) x 337

Rooms Size (Sq ft) Tonnage Capacity Up to 90 sq ft 0.8 Ton Up to 120 sq ft 1.0 Ton Up to 180 sq ft 1.5 Ton Up to 220 sq ft 2.0 Ton Visit www.compareindia.com

The output capacity is a measure of the amount of heat that will be removed (cooling) or added (heating) to the room/s in your house by the air conditioner. The output range you need will depend upon your particular requirements. Air conditioner outputs are measured in kilowatts (kW). As an approximate guide for sizing a room unit allow:
125watts (0.125kW) per square metre of floor area to be cooled in living areas;
80 watts (0.080kW) per square metre of floor area in bedrooms.
These estimates depend on the climate and the efficiency of your house design (orientation, glazing and insulation levels).
It is advisable to get a full heating or cooling load calculation from an authorised air conditioning installer or manufacturer before you buy

For selecting a proper AC you need to know several things, like

1. Its application, e.g bed room, class, laboratory, office etc etc.
2. The room to be air conditioned is under bare roof or there are room over it.
3. Location and number of doors and windows viz east, west etc.
4. Building material and its heat conduction coefficient.
5. Number of occupants.
6. Light load.
7. Any heat source present or not and its wattage.
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