How to select right capacity (Ton) Air-Conditioner (AC) !!!

Air Conditioners has become one of the necessary appliances to overcome summer heat waves. Many of us plan to buy air conditioners but confused about which tonnage of AC to be purchased. Selecting low capacity machine will make you feel that the cooling is not sufficient and higher capacity will result in higher energy bills. This article will help you to select correctly sized air-conditioner to suit your requirement. 

Cooling capacity of any air conditioner is measured in BTU/hr. 

• 1 Ton = 12000 BTU/hr 
• 1.5 Ton = 18000 BTU/hr 
• 2 Ton = 24000 BTU/hr 

Actual BTU/hr of a model can be viewed in product catalogue / company website of manufacturer which you prefer to buy. 

Generally we heard tonnage selection based on square feet of room, in order to select correct tonnage we have to consider other factors like height of the room, number of occupants in the room, lighting of the room, appliances that generate heat, etc. 

Air conditioner cools entire room not only the surface area so calculate the volume of the room, volume = Length (ft) x Width (ft) x Height (ft). Multiple the volume in cubic feet by 6. Resultant value is the BTU/hr required to cool the room without considering other factors like number of occupants, appliance that generate heat etc. 

Cooling load of 500 BTU/hr has to be considered for each occupant. In case of couple bedroom it shall be 1000 BTU/hr whereas for living room of a family of 6 would require 3000 BTU/hr. 

Refrigerator is one of the appliances which is available in all household now-a-days, a refrigerator of 125W releases heat around 2000 BTU/hr. 

Now we shall calculate BTU requirement of living room of size (20 ft x 15 ft x 10 ft) for a family of 6 members having refrigerator (125 W) in their living room. 

Volume = 20 x 15 x 10 = 3000 cubic feet 

BTU required by room = Volume x 6 = 18000 BTU/hr 

BTU for 6 occupants = 6 x 500 = 3000 BTU/hr 

BTU for refrigerator = 2000 BTU/hr  

Total BTU = 23000 BTU/hr 

2 Ton machine provides 24000 BTU/hr cooling capacity, family may select 2 Ton machine for their living room considering this. 

We also need to make a note of lighting of room, east or west facing of room also plays a role in cooling requirement. In above example we have not considered the same. In general 10% extra load of cooling requirement is always preferred to take care of these kind of variations and higher ambient in summer. Considering this 23000 + 10% = 25300 BTU/hr will be required to cool living room. 

Family needs to select a model above 2 ton for their living room, which can be 2.25 Ton (27000 BTU / hr) or 2.5 Ton (30000 BTU/hr) based on the model availability in market. 

Hope this article clarifies on how to select right capacity (ton) air conditioner. If you have any queries or comments, please post here.