What size AC unit do I need for my home?

ac unit size

Air conditioners are the best way to keep your home nice and cool.

When it comes to choosing the right AC unit there are many different models and styles. To find out what size AC unit you need for your home you need to understand BTU measurements.

What is BTU?

A British Thermal Unit is a measurement that’s used to work out the heating or cooling properties of a home appliance. To explain further, 1 BTU is needed to raise water temperature by 1° F, and this is based on one-pound of water. 

All air conditioners are given a British Thermal Unit rating, the rating is an indication of how powerful the appliance is. BTUs measure how much energy it takes to raise the temperature of the water, since air conditioners are for cooling, you might be wondering how BTUs are relevant?

Air conditioners work by removing the heat from the air and then circulating cool air back into the room. For air conditioners, BTUs measure the heat that’s removed, instead of the heat that’s added. A high BTU rating indicates a powerful air conditioning appliance.

What size AC unit do I need for my home?

When you are choosing an air conditioner it’s important to get the right size unit for your home. To choose the right air conditioner size unit you need to find the correct BTU rating. You should find out which BTU rating you need depending on the measurements of your home in square foot.

To calculate the size, you need to determine the size of the area that requires cooling. First, multiply the length of the room by the width. Depending on the model, air conditioners need approximately 20-25 BTU per square foot.

According to Energy.Gov, “an air conditioner generally needs 20 BTU for each square foot of living space.” Based on this approximation, you can then multiply the room size in sq. ft by 20BTU.

For example:

If you need to cool a room that’s 10 feet wide and 14 feet long, you calculate 10 x 14 to get 140 square feet.

Next, you multiply 140 sq. ft by 20BTU. For this room, you’d require an air conditioner with a 2800 BTU.

How do I calculate which air conditioning unit I need in tons?

Perhaps you require an air conditioning unit to cool your entire home? In this case, you need to work out the total size of your home in square footage.

To do this you can combine the calculations in sq. ft for each room (and the hallways). 

Many modern air conditioners measure the output in tons. To convert the total BTUs into tons you need to divide the square footage (for the entire home) by 12,000. According to Hunker, “A 1,650 square foot house equates to approximately 3.5 tons. The calculation is based upon multiplying 1,650 by 25 to get the approximate BTU needs and dividing the total by 12,000.” Additionally, a ‘1,600-square-foot home will generally require a 3-ton air conditioning unit.

As you can see, the above calculations are based on an air conditioning unit that operates at 25BTU per square foot. To choose the right air conditioner size, you must first measure your home.

Why is it important to choose the right air conditioner size?

Choosing the wrong size AC unit can cause many problems.

If your air conditioning unit is too small, the unit will overexert resulting in uneven temperatures, excessive use of energy, and frequent wear and tear. Your bills may increase and your air conditioner is likely to break down eventually.

When your air conditioning unit is too big you may have an issue with short-cycling, meaning the unit cools the area too fast and then switches on and off. The unit is unable to continuously run for long enough to filter and dehumidify the air. 

There are a few other factors that you should consider when choosing the right air conditioner:

  • Your location: The type of air conditioning unit you need depends on where you live and how hot it is there.
  • Insulation: Ceiling insulation directly affects the thermal efficiency of your property. Consider the insulation of your walls and ceilings when you are choosing your unit.
  • Room orientation: If you are having air conditioning installed in one room, consider the direction that the room faces. A west-facing room will experience different natural light and temperature compared to a south-facing room.


How can Roscoe Brown help?

At Roscoe Brown we have a wide range of air conditioning units to suit different homes and workplaces. Whether you need a new installation or a maintenance job we’ve got you covered.

For more information on choosing the right air conditioner size for your home contact us today.

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