Cooling Capacity and AC Size

May 24, 2020

Cooling capacity is a term in the HVAC industry that can save you money, as well as help you pick the right size AC for your home. But what is cooling capacity? and how does the lack of it impact your lifestyle?

Keeping your home cool during the summer months is imperative to the health and well-being of most people. While it is possible to live without the luxury of central cooling, there will be many sleepless nights, extra laundry, and overall discomfort.

If you must suffer from the elements while in your own home, then why even build a shelter in the first place? Therefore, it is equally as important to make sure to buy the appropriately- sized air conditioning unit fit for your situation.

Guessing and opting for the ‘bigger is better’ mentality, or likewise, being frugal and choosing the smallest air conditioner for practicality can wreak monetary disaster. Instead, cooling capacity is used to measure the most efficient size AC unit for a home. 

Air Conditioner Size and Cooling Capacity

To get the most efficiency out of an air conditioner, it is imperative to measure the square footage of whichever home/ apartment/ condo that the device will be cooling. In the case that one was to buy an air conditioner that is too small, then there will be the problem of the device not being able to cool the entirety of the home. Perhaps it’d be able to fill out only one room with cold air, or just a little further than that, however the rest of the house is left to be a humid mess. In this scenario you have just paid for a plug-in fan for the price of an air conditioner.

A wall of window air conditioner units in an apartment building
“Rattlers” are a common addition to apartment buildings, as they are the most efficient for the limited sq/ft per room.

The opposite scenario is more of an ‘overkill’ situation, where one opts to buy an unnecessarily large unit with the thought process that more power is always better. In one way, yes, it is correct. A large air conditioning unit will certainly keep a smaller home completely cool, at a hefty charge on the monthly energy bill. The previous example was illustrated as buying a fan for the price of an air conditioner, however in this case buying an overly large air conditioner for a smaller house is like buying a $4000 computer to play pac-man on. Either situation does not make financial sense for the output. Likewise, paying for hydro is already an expensive problem in Ontario, so paying for an over-priced air conditioner does not help in the least when this error can be revoked by a few minutes of measurement.

cooling walking down a grey hallway with large metal ducts above him
Larger buildings will require bigger air conditioners since they have a higher cooling capacity to fulfill.


Measuring the cooling capacity of your home sounds complicated, however it is much easier than the name suggests. No need to calculate PPM, volume, or thermodynamic gas exchange; Instead, utilize basic third grade math to calculate the floor surface area with a standard length x width formula.

Length x width =  Total area (sq ft)

The resulting total can then be compared to a guide of ‘basic cooling capacity’ which is marked for each size-specific air conditioner. With this, it is possible to get the best-possible estimate, and thus the most efficient for the amount of money you spend each month. For additional help, there are plenty of online resources in the form of charts and calculators that can help calculate cooling capacity, or ‘BTU calculations.

Square Feet BTU’S Per Hour

100 to 150   -5000

150 to 250   -6000

250 to 300    -7000

300 to 350 – 8000

350 to 400 – 9000

400 to 450 – 10,000

450 to 550 – 12,000

550 to 700 – 14,000

700 to 1000   – 18,000

1000 to 1200    – 21,000

1200 to 1400 – 23,000

1400 to 1500    – 24,000

1500 to 2000    -30,000

2000 to 2500 -34,000

This can be used to accurately find the proper-sized air conditioner fit for your specific living situation. The cost-effectiveness of this cannot be understated, so use it to your own advantage.




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Providing Residential and Commercial Plumbing, Heating & Electrical Services in London Ontario