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Oregon Ductless’s Mini Split Sizing Chart

May 13, 2022

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Mini Split Sizing Chart

Ductless mini-split HVAC systems are highly efficient solutions that use inverter technology to provide just the right amount of heating and cooling. They fit compact spaces, which is an advantage over just about any other air conditioning solution. But like any other, they need to be sized properly for your home. Our mini-split sizing chart will help you find the right system; and first, we’ll look at how mini-split system sizes are determined. 

  • Square Footage: To calculate a room’s square footage, measure its length, and then its width. Multiply the two numbers to determine their size. Using this formula, a room that’s 20 feet long by 20 feet wide is 400 square feet (sq. ft.). Be sure to add in the size of closets and other spaces within the room. 
  • British Thermal Units (BTU): Measuring thermal energy, a BTU is equal to the power needed to change the temperature of one pound of water by 1℉. Mini-splits generally range from 6,000 BTUs to 56,000 BTUs. 12,000 BTUs is equal to 1 ton; a 1-ton system can cool or heat a 450 to 550 square foot space.

Importance of Size

Bigger is never better when it comes to HVAC systems. If the system is too big, it will draw too much power, run for too short a time, and increase energy costs. An undersized unit will run continuously, while not providing adequate cooling. It will need more capacity to run as well. Oversizing or under-sizing a system is never good.

Min-Split Sizing Chart 

Mini split sizing chart

Other Load Calculation Considerations:

While room size is the greatest influence over BTU capacity, there are many other factors for determining the ideal mini-split system size. These include: 

  • Climate: Increase the BTU rating by at least 30% in areas that regularly see temperatures over 90℉ during the hottest months of the year. Extremely high or low temperatures can affect the temperature indoors. 
  • Age/Insulation: Newer homes are typically better insulated than older ones. Poor insulation means your home will require more power for heating and cooling. If the quality of insulation is subpar, you’ll need to increase the BTU rating by at least 30%. 
  • Ceiling Height: In most homes, ceilings are about 8 feet high. If your home has higher ceilings, the rooms will be larger, requiring at least 20% more BTU capacity for heating and cooling. 
  • Sunlight: A room that receives direct sunlight tends to be warmer, and requires more capacity for cooling, meaning a more powerful mini-split is required. 
  • Windows/Doors: Are not insulated, so the more there are in a room, the more BTU capacity you will need. Air leaks from cracks and gaps in door or window joints affect performance as well.
  • Floor Type: Carpeting has insulating properties, reducing the required load, but a mini-split must work harder if you have tile, stone, or hardwood floors. 
  • Heat Sources: In addition to sunlight, other heat sources include lightbulbs, kitchen appliances, and people (the more people occupying the room, the bigger the mini-split you’ll need to maintain a comfortable temperature).

Contact Oregon Ductless

Our mini-split sizing chart is a reference to help decide on the best system for your home. For help choosing and installing a ductless heat pump, or to schedule repair or maintenance, request an appointment by calling 503-878-7339 today.

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