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How to find the right air conditioner capacity for your home ?

Summer is here and it’s time to replace your old air conditioner. It’s easy to get overwhelmed with all the information out there about find the right AC for your home. The one feature that you really need to get right is the capacity.

Meaning of “Capacity”

What does this term mean, in the context of air conditioners (ACs)? In lay man’s terms, it is how powerful the air conditioner is i.e. how much cooling it can provide. It is generally measured in "tons" or British Thermal Units (BTUs). During the days when ACs were still not invented, people would use "tons" of ice to keep their homes cool. Hence, "tons" became a uniform measurement of the cooling quotient of ACs. A ton is the amount of heat the AC can remove within an hour. The modern day unit of measurement is BTUs that is generally written on the label on the condenser unit of your AC. To give you a better perspective, one BTU is the heat that is produced when a single matchstick is burnt all the way. Capacity is one crucial factor that depends on the specification of your home.

1) Factors that determine the capacity

The capacity of an air conditioner depends upon:

  • Climate

  • Outdoor humidity

  • Room size

  • Ceiling height

  • The construction material of home

  • Floor level

  • Number of people in the house

  • Time of operation

  • Insulation level in the house

  • Windows area

  • Air leakage inside the house

  • Landscape

  • The heat generated by other pieces of equipment

2) Capacity calculation

Bigger is not always better. A bigger AC that is not a fit for your house area can impact the cooling efficiency and operating costs. Hence, the capacity has to be calculated carefully. A few things to keep in mind are:

1 Ton = 12,000 BTUs per hour = Amount of heat required to melt a block of ice in one day that weighs a ton.

Step1 - Calculate the area of the household to be cooled

If the room shape is square-rectangular like, Area = Length x Breadth.

If the room shaped like a triangle, Area = Length * Breadth * 1/2.

If the room is shaped oddly, divide it into known figures, calculate the area of each and then sum it up.

You will get a value in square feet.

Step 2 - Here is an AC capacity chart* for your referral


*This chart assumes that there are 2 occupants, average sized windows, medium insulation and sun exposure, keeping all other factors constant.

**some values are approximate

Step 3 - Add more tonnage in the following cases:

More than 2 occupants - Around 600 BTU/Hr. for every additional person

Temperature higher than 45 degrees- Approximately 6000 BTU/Hr

Space includes a kitchen or a very hot area- Around 4000 BTU/Hr

In a few cases, tonnage can also be subtracted. Remember the factors we mentioned before. Use your judgement to avoid under sizing and oversizing. Treat this chart as a rough guideline.

Step 4 -Extra factors to consider

After getting a rough idea about the capacity, there are certain other factors that should be taken into account -

  • Two styles of ACs are available-one that fits a 120 Volts outlet configuration and one that fits a 240 Volts outlet configuration. Do not buy an air conditioner incompatible with the outlet.

  • Many times, a combination of ACs with smaller BTUs is viable if the room is large, but window openings are small. In that case, each AC requires a different electrical outlet.

  • The bigger the BTUs, the bigger the size of the AC.

  • Different models of ACs offer different ranges of capacity. Every model has differentiating features which we will discuss now in the article.

3) Types of air conditioners

There are different models of ACs that one can choose from. The capacity varies from model to model.

  • Window ACs

- These are ACs that require an open window or a large hole to fit into. This type is one of the older and more affordable options, ideal for smaller spaces. They come in sizes ranging from 0.75 tons to 2 tons. The cooling effectiveness, however, is subject to many conditions. The AC should fit in the window. Measure the height and width of the open window so that the maximum space is available for calculation. Lookout for charts on the side of each box of the window AC that displays the opening size requirements. New style window ACs are more energy efficient if your focus is on lower electricity bills.

  • Split ACs

- They are more aesthetic and a less noisy alternative to window ACs. They are installed at a height that filters the cold air better and causes thorough cooling. They have two units - indoor and outdoor, which makes the system more compact. The size is not always commensurate with the capacity in this case, as most of the unit is outdoor. The capacities available for this type range from 1 ton to 5 ton.

  • Freestanding ACs

- This type is more portable and can be easily installed. They need to be plugged in near windows. They are available from 1 ton onwards.

4) The problem of oversizing

Buying an AC which has too big a capacity for the room is not a good idea. An oversized AC can adversely affect cooling. These are the various problems that occur

  • The AC switches on and off too often. It doesn’t complete its cooling cycle. It senses the temperature change around the AC faster than normal and it switches off in less than 10 minutes. The cycle should last between 20-30 minutes. Hence, it’s not able to cool the parts of the rooms that are far away.

  • An AC performs two functions - cooling and dehumidification. A bigger AC will cool fast but doesn’t dehumidify at the same rate. Moisture is still left in the air.

  • Oversizing can also cause the expenditure of more energy and unnecessary load on the machine that can reduce the lifespan and increase electricity charges.

5) The problem of under sizing

  • Under sizing causes the AC to run continuously without any intervals. It fails to reach the temperature on the thermostat and tends to cycle for more than 30 minutes

  • It affects the cooling effectiveness and airflow. Naturally, the area will never feel cold enough, or there will be temperature inconsistency.

  • The unit will continuously try to match the temperature set on the thermostat. This activity will put undue pressure on the AC and will increase energy bills in the process.

6) Points for further consideration

  • If the cooling capacity required is more than 12,000 BTU/Hr, you can consider two smaller units if more sockets are available. Check the volt of the circuit that is required for installation before buying an AC.

  • Basements, attics, stairwells and kitchens require different capacity compared to bedrooms or living rooms.

  • If a single AC doesn’t provide sufficient cooling, consider supplemental cooling with an AC which has a lower capacity.

  • Look for a higher Energy Efficiency Ratio when buying an AC. It is the ratio of the capacity to the power input (watts). The Energy Star label is a standard certification for ACs that do well on this parameter.

  • The cooling is not only based on capacity. There are many new types of ACs like Inverter based ACs that offer more efficiency at a higher price. WIFI ACs have better functionality as they allow control of the AC from any location and can cause greater cooling. An environment-friendly and cheaper option than ACs is an air cooler that provides similar cooling.

  • Are you concerned about installation? Don’t worry, we take care of any type of AC installation for free. You can even exchange your old split or window AC with us and get a discount on your new purchase.

To sum it up, buying an air conditioner requires a lot of deliberation. Assess your needs thoroughly and keep in mind these points for making the investment last. To buy the perfect air conditioner for your home and to get great advice, you can visit one of our retail outlets near you or call us at 8001279999 for assistance.