How to Size Ductless Heat Pumps?

How Do I Know What Sized System My House Needs?

Ductless systems are sized to meet the heating and cooling needs of a home’s individual zones. There is a great deal of flexibility when it comes to system sizing as one indoor unit can provide between ¾ and 2 ½ tons of heating/cooling depending on its BTU capacity rating. Some common capacities for indoor units are 9k, 12k, 18k, 24k, and 30k BTU. Outdoor units are sized to meet the combined load of all heating/cooling zones. More than one outdoor unit may be necessary for multi-zone systems.

Why Is Ductless Heat Pump Sizing So Important?

If you're considering a ductless split system installation, you probably have some questions. Proper ductless air conditioner sizing is essential for high efficiency performance and the level of cooling capacity. If the sizing is too small or too large, the system won't cool properly, and it won't operate efficiently. And if the system is improperly sized, if the indoor units are mounted in the wrong locations, or the installation itself is done incorrectly, you'll be left with an expensive problem to fix. Systems that are incorrectly sized and improperly positioned can seriously interfere with humidity control and cost a bundle in high electric bills.

Ductless splits cool a larger area at the same BTU level than do window air conditioners and portable air conditioners. Below is an Approximate Sizing Guide:

350 square feet = 9,000 BTU

500 square feet = 12,000 BTU

750 square feet = 18,000 BTU

1000 square feet = 24,000 BTU

1250 square feet = 30,000 BTU

1500 square feet = 36,000 BTU





Variables that Reduce an Air Conditioners Useful Area:

Climate: If you live in an area of the world that has seasonal temperatures in excess of 90° F. Increase 30%.

Windows: If you have south facing windows in your designated area, or if you have large windows. Increase 20%.

Ceiling Height: High ceilings increase a room’s size reducing the air conditioners effectiveness. Increase 20%.

Appliances: Heavy kitchen appliances and electronics increase the heat created in an area. Increase 20%.

People: The more people in the area the more heat produced. Increase 20%
6. Insulation: Poorly insulated homes are much more difficult to cool or heat. Increase 30%.

Example:

If our area is a 16’ x 16’ room (256 sq. ft.) in Orlando, Florida (Increase 30%) with south facing windows (Increase 20%) you would need an air conditioner that can cool a 384 sq. ft. area.