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Mini Split Sizing (with Calculator)

Mini Split Sizing (with Calculator)

Jon Hubal
4 minute read

So you want to go ductless, realizing a mini-split will solve all your climate control needs – but now you have to figure out how to size your mini-split sizing.

Have no fear. Sizing the correct unit is simple. Our mini split sizing calculator and mini spit sizing chart will help guide you to the correct mini split size for your home.

Sizing Your Ductless Mini-Split

The total area you want to condition (sqft) determines the required heat output (BTU/hr), determining the unit size you need. 

The total area is the square feet of all the rooms added together. You need the total because this is how much energy the outdoor condenser unit will need to sufficiently service all your areas.

Using Sizing Calculators for Mini Split Systems

Once you have your total square footage, using a sizing calculator is the easiest way to do this. Licensed technicians have already done much of the math for you – why not take advantage!

There are simple charts that take just your square feet and tell you what BTU/hr you need, providing a quick and relatively accurate assessment (seen below). 

Mini Split Sizing Chart

mini split sizing chart

The Basics of Mini Split Sizing

Ductless minis are known for their efficiency, but only if you size the suitable unit for the space required. Sizing the right mini is the most critical part of installing one.

Avoiding Oversized or Undersized Units

Bigger isn't always better. If your mini system is oversized, you'll waste money on an unnecessarily large unit and risk high utility bills. Overpowered units suffer from short cycling, quickly turning on and off, using more energy, and wearing faster over time. 

If your system is undersized and can't effectively condition the space, that's a big issue. They'll work much longer and harder than they should, and like oversized units, they become incredibly inefficient and wear much quicker. 

Let's start by understanding how units are measured in HVAC.

How to Size a Mini Split System

The size of a system refers to how much heating or cooling it can provide every hour. Conventionally used for heat, BTU (British Thermal Units) is the standard measurement of temperature in the industry. In technical terms, it measures the energy required to change one pound of water by one degree Fahrenheit. In layman's terms, it measures how much energy your air conditioner uses to add or remove heat from your home.

You must determine how many BTUs you need per hour – or BTU/hr. 

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Calculating Mini Split Size: Measuring Your Space for Accurate Sizing

How you get, there is by figuring out the size of the space you need to control. This means measuring the area of all the rooms you want conditioning. Achieve this by multiplying the length of the individual room by the width.

This will give you the square foot area – or sqft, the standard measure used for ductless system sizing.

If you have uniquely sized rooms or desire to be as efficient as possible, calculating the square foot area with the room height (sqft x room height) can provide a more accurate estimate for your actual energy needs. 

Sizing Mini Split System

Though it may sound daunting, sizing a ductless HVAC system is much easier than you think. With fairly simple calculations, there is not much math involved, and there are plenty of useful charts and calculators designed by certified pros to help you along the way. 

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