air conditioner

It’s getting hot out there, and when mother nature turns the heat up outside, it’s time to cool it down inside with an air conditioner. But not all cooling units are the same, and if you want to bring one home and cool your space properly, you have to choose the right size.

How do air conditioners work?

window air conditionerAir conditioners are made up of an evaporator, compressor, condenser, and an expansion device. They work by using a chemical inside the unit that cycles inside and outside to remove heat and replace it with cool air.

There are two types of air conditioners. You can find window air conditioners that sit inside the frame of your window or portable air conditioners that you can move from room to room.

There is one thing you should note when you’re using portable cooling. Portable units include an exhaust hose that will vent warm air and moisture, so you’ll want to ensure you have a window nearby to drape the hose out of.

What you should consider before you buy an air conditioner

danby air conditionerAir conditioners not only remove heat from the air, but they also remove humidity. When sizing your unit, you need to take into account exactly what size of room you’d like to cool.

If you choose an oversized unit it will cool your room more quickly, but it won’t do a good job of removing the humidity. That could leave your room feeling damp and clammy, and if your room is damp you could end up with problems with mold and fungus.

Having a properly sized air conditioner means it will reduce humidity very effectively as it cools, so sizing your space and choosing the right BTU is important.

Calculate the size of your space

Take a look at the room you’d like to use the air conditioner in. Most rooms are rectangular, so to get the measurement it’s simply length times the width of the room. If you have an odd-shaped room you may have to calculate the square footage by splitting the room into rectangles and triangles, then taking the area of each and adding them up.

What should your air conditioner BTU be?

Cooling capacity is measured in BTU’s (British Thermal Units) per hour. The higher the BTU rating, the more powerful the cooling power.

The first step in determining which BTU is for you is to calculate the size of your space. The next step is to use the following table to determine the standard BTU sizing for the room you want to cool.

What to take into account when choosing BTU

To get the most out of your unit and ensure it will cool the space you want to cool, you need to be as close to the right BTU as possible. That means taking into consideration the amount of extra heat in the space you are cooling.

These are a few adjustments you should make when selecting the right BTU.

  • If the room you’re cooling has constant sun, add 10%
  • If the room is heavily shaded, reduce by 10%
  • If the room is a kitchen, add 4,000 BTUs
  • If the room has high ceilings that are 10 feet or higher, add 10%
  • If the room is regularly occupied by more than two people, add 600 BTUs for each person above 2

What is an Energy Efficiency Rating?

The last thing you should consider is the EER (Energy Efficiency Rating) of the air conditioner. The EER lets you know how energy efficient the air conditioner is to operate. EER rating is simply calculated by dividing the BTU of an air conditioner by its wattage.

Air conditioners with a high EER rating will use less electricity to create the same amount of BTU’s of output. Another benefit of a higher EER is it likely has a better compressor and runs more quietly than other models.

Ready to cool off?

Now that you know what you need to consider when buying a unit to cool your home, you’re ready for a long, hot summer. Check out all of the air conditioners and fans available on Best Buy. They carry all types from Danby, Haier, De’Longhi, Insignia, and Honeywell.

If you’d like to know how to install your air conditioner, take a look at this post.

Choose from portable air conditioners you can wheel from room to room or window air conditioners to keep your bedrooms cool and enjoy a cool breeze when the temperatures start to soar.


  1. I live in a three bedroom apartment building. I am confused as to what air-condition to buy.

    3 air conditioners or one? How much hydro am I expected to pay if I have three air conditioners?

  2. The portable units still need to be vented to the outside. You should not run them without the exhaust hose being vented out a window.

  3. These portable air conditioners are designed to work inside without direct access to outside ventilation. They will work well placing them anywhere inside.

    • This is not true! All of the portable units Best Buy sells need a window to exhaust the hot air (and sometimes the water vapor depending on the model). You cannot just place them in the middle of a room and expect any cooling! OMG If there is no window, you can create a hole through the wall to the outside. But you must vent to the outside in some manner.

  4. Do this portable air conditioner “not window units” require outside ventilation, please let me know

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