What Size Window Air Conditioner Does a Small Room Need (BTUs)

By | June 9, 2024

What Size Window Air Conditioner Does A Small Room Need
Large whole house air-conditioning units are great for cooling an entire home, but what if you only have a single room, such as a bedroom, that only needs to be cooled down?

Small window-mounted air-conditioning units come in a variety of sizes and packages.

The small cooling units are placed in a window that is enclosed and cools the room it is placed in.

Most small room window air conditioners are 6,000 BTUs or less.

How To Size a Window Air Conditioner Cooling Capacity to a Small Room

How To Size a Window Air Conditioner Cooling Capacity to a Small Room

  • 50 to 100 Sq Ft 5,000 BTUs
  • 150 to 250 Sq Ft 6,000 BTUs
  • 250 to 300 Sq Ft 7,000 BTUs
  • 300 to 350 8,000 BTUs

The way to determine what size of the small air-conditioning unit is needed is to measure the square feet of the room. This is done by measuring the width and the length of the room and multiplying it.

So a room that is 10 feet wide by 15 feet long would be 150 square feet.

Air-conditioning unit’s cooling capacity is measured in BTU (British thermal units), which are labeled in every air-conditioning sold.

To get the amounts of BTUs, you will need to apply the square feet of the room by 25 BTUs. So a room that is 150 square feet X 25 = 3750 BTU.
How To Size a Window Air Conditioner Cooling Capacity to a Small Room 2
So for this example, the 10′ x 15′ room would need an air-conditioning unit that puts out 3750 BTU.

This can be rounded up depending on how well the room is built as far as insulation and how often the doors are open and closed.

Getting a unit that is much larger than necessary is not a good thing when it comes to air-conditioning. The same can be said for getting a unit that is smaller than necessary.

An air-conditioning unit that is larger than needed will have bigger components, mainly the compressor, which will use more electricity than is needed.

Often what happens when a window air-conditioning unit is oversized where room it will kick on and off more often the needed?

The initial start times of an air conditioner as a large power draw which, to constant cycling, will run up a power bill more than necessary.

A unit that is smaller than needed will run longer and is not constantly running up the electricity bill.

So when sizing a small window air-conditioning unit’s be sure to measure the width by the length and then multiply it by 25 to give the number of BTU necessary.

Category: window mounted air conditioner

About Aaron H. Benetti

Aaron H. Benetti an HVAC technician who has worked in the field since 1991. He began his career as an HVAC installer and later began doing troubleshooting and repairs. Around 2010, he began to write books on HVAC topics, mainly tutorials and how-to information. Currently, Aaron works as an HVAC tech and also writes many articles and posts for websites as well as books and videos on HVAC topics.

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