Today, Air Conditioner has become a necessity which was once a luxury especially during hot and humid summers here in India. Hence an AC helps create a calming effect right in your room to make one feel relaxed.
Selecting an AC is easy with right information. Most of the times people go wrong in choosing an AC without considering the size of the room. Sizing is an important step before buying an AC. You get the sizing wrong and you will face problems like insufficient cooling, less moisture removal and unwanted high electricity bills.
Air Conditioner comes in different sizes and capacities, weather Window AC, Split AC or central AC. These units should cool the required area of your home with maximum efficiency. How do you do that? Just by measuring the area of the area required to cool and with simple mathematical calculation, it can be done.
Most air conditioners are rated in BTU per hour (British thermal unit) or by tonnage. One ton is equal to 12,000 BTU per hour. In India, we usually measure in tonnage.
To calculate, multiply the length and breadth of the room, take square-root of the product and divide by 10.The resulting number will give the desired tonnage.
To make it clearer let us say
So basically for a room which is 150 square feet, we need to get 1.2 ton AC.
- The room is 10 feet wide by 15 feet long.
- That means 10×15=150 square feet.
- Take the sqrt(150)/10
- We get 1.247
- Choose an AC which is 1.2 Tonnes.
Choosing the right tonnage is very important.
Still you may have a doubt what happens if low ton or a large ton is used for a smaller or a bigger area. Here is what happens. Smaller ton will continuously run in a larger area as it will take time to cool the place. This will increase your electric bill and effectiveness of cooling will be minimal.
A large ton (more than required for the area) air conditioner can be oversupply. An air conditioner too large will cool quickly, but that may be difficulty to work because along with cooling the air, the air conditioner also removes the moisture from the air .Though the air may be cooler, if the unit doesn’t run long enough, the moisture cannot be extracted from the air properly. This will result in Sticky and clammy feeling.
Apart from the above tonnage we need to consider other factors as well like
- Whether the room walls are directly exposed to sunlight.
- Average number of persons staying in the room. (If more people)
- Whether the room is located in the top floor i.e. a terrace is above your flat.
- Outside temperature during summers. (Average ambient temperature)
- If the room is nearer to the kitchen and AC is required for the same or a room which has appliance which produce heat like LED, Desktop etc.
For all the factors above you may need to go for slightly higher capacity than the calculated tonnage. The Tonnage will vary accordingly, more or less a half ton more than the calculated tonnage should do. But in some extreme cases where the temperature is extremely high you may require more tonnage.
- Make sure that you install the unit in an area not exposed to rain or direct sunlight.
- Make sure that you install the unit in an area that provides good ventilation. Airflow should not be blocked.
- Bureau of Energy Efficient rates AC with stars (Reliable). Buy the one with more stars as they are more energy efficient. More stars the better.
- Make Sure the room is well insulated. Cracks, crevices around window frame are responsible for cool air to escape. Use curtains to cover the window for air retention. Loss of air through these places will increase electricity bills and lessen cooling effect.
How to calculate AC tonnage for room size
How to choose the air conditioner size based on room size and conditions. Take into account the room dimensions and other factors like climatic conditions.