What Size Mitsubishi Mini Split Do I Need for My Home?

Mini split heating and cooling systems are growing in popularity because of their many advantages over central heating. Mitsubishi, an HVAC industry giant, makes powerful and efficient ductless mini split systems. 

These systems use inverter technology to accurately heat and cool rooms to the desired temperature and humidity. For the best results, a Mitsubishi mini split multi zone HVAC system must be properly sized to meet the needs of the rooms it is used in.

To match your home’s heating and cooling needs with the right size Mitsubishi mini split, you need to understand British Thermal Units (BTUs) and how they relate to room size. 

There are also home-specific considerations, like floor type or ceiling height, that alter the original calculations. Using the wrong size mini split can lead to expensive inefficiencies, premature maintenance, and an uncomfortable home, so it is vital to get the sizing right.

Too Big vs. Too Small 

Your HVAC system is inefficient, whether your mini split unit is too big or too small for an area. If it is too small, it will run continuously and fail to heat or cool its assigned zone. Besides being uncomfortable, this is expensive because the system uses more energy than it would if it were sized correctly. 

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A system that is too big is also inefficient and expensive because it short cycles. Short cycling is when a wall-mounted air handler heats or cools a zone so quickly that it constantly turns on and off. 

Short cycling prohibits a mini split system from dehumidifying the air, leaving a room feeling damp instead of comfortable. Plus, short cycling increases the chance of malfunction, which costs homeowners money on maintenance. A properly sized mini split system is essential to the unit’s longevity and efficient operation. 

British Thermal Units

If you have been looking through online catalogs of HVAC systems, you have likely come across the British Thermal Unit (BTU) designation that each system has. A BTU is the amount of heat required to raise the temperature of a pound of water by one degree Fahrenheit. 

It is a standard measurement of a system’s heating and cooling ability. The higher a system’s BTUs, the larger an area it can efficiently heat and cool. 

From BTUs to Square Feet

The conversion from a system’s BTUs to the appropriate room size for the mini split system starts with a general equation, but other factors add complications. Since it is so important to correctly size your home’s mini split AC units, a technician handles these calculations for you; To make the estimation yourself before bringing in a professional for installation, follow these steps. 

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1. Measure square footage.

Calculate the room's square footage that a Mitsubishi AC Unit will be responsible for heating and cooling. For a rectangular room, multiply the length and the width to find the square footage. Triangular and circular rooms require more advanced math, but there are online tools available to help.

2. Convert to BTU.

Multiply the square feet number by 20 to convert the room’s square footage to BTUs. A 1,000 square foot room requires a mini split system with a wall-mounted air handler with 20,000 BTUs. 

If no extraneous factors are present, this calculation gives you the correct sized system for a room. Repeat this process for all rooms/zones where you want your Mitsubishi mini split to provide HVAC services.

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3. Consider complicating factors.

There are many factors beyond square footage that change the conversion number, including the outside climate, a home’s insulation, and the qualities of the specific room. If it is consistently very hot or very cold, you will need a larger system. For instance, a climate consistently above 90 degrees Fahrenheit increases the square footage to BTU conversion number from 20 to about 33.

If a home has poor insulation, it will likely require a larger mini split system. Poor insulation is common in older homes, making heating and cooling a home less efficient. This leads to about a 30 percent increase in BTUs to accommodate the home’s inefficiencies.

Finally, the room can affect the mini split size with large windows, direct sunlight, large appliances, and floor type. 

With the help of a professional, your Mitsubishi mini split system keeps your home comfortable without any wasted energy.

ComfortUp Has Mini Splits of All Sizes

Whether you need a single room small wall-mounted AC unit or you want to outfit your whole home with a multi zone mini split system, ComfortUp has the HVAC solutions for you. You can narrow down what size system you need, or contact us and talk with an expert to find the perfect size of Mitsubishi mini split for your home.