What Size Mini-Split Do I Need?

If you’re considering installing a mini-split system, a ductless AC system that uses refrigerant to transfer hot and cool air, you’ll need to get the right size to cool down or warm up effectively. So, what size mini-split do you need?

The answer depends on the square footage of your space and several other factors, including the climate you live in and your ceiling height. Let’s review common mini-split sizes, how to measure the right size for your home, and when to hire an AC installer to place your new cooling system.

What Is the Standard Mini-Split Size?

The most common size of mini-split has 12,000 British thermal units (BTUs) to heat an average-sized space. BTUs measure the energy it takes to remove heat from indoor air and determine which size mini-split works best for your home. Mini-splits that are too small will run continuously and be overworked, while oversized units will short cycle, which can not only increase your energy bills but also require more regular maintenance and shorten the unit’s lifespan.

Mini-Split Size by Square Footage

The square footage of the space you’re trying to heat or cool is crucial in determining which size mini-split unit will work best. The larger the square footage, the more BTUs you’ll need. However, it’s important to note that a mini-split won’t work for a space larger than 2,500 square feet.

How to Measure the Right Size Mini-Split

Measuring your home for the right size mini-split can be a bit overwhelming, especially if math isn’t your strong suit. You can enlist the help of a professional air conditioning installer near you to measure room dimensions and determine which size unit will work best for your space. However, if you’re confident in your measuring abilities, the steps below can help you figure out the right size mini-split. 

1. Calculate Square Footage

For square or rectangular rooms, you’ll need to measure the length and width of the space and multiply the two figures together to get its square footage. For example, a 14- by 14-square foot room will be 196 square feet. For round rooms, you’ll need to measure the distance from the wall to the center of the room, then multiply that number by itself, then by pi (π). For example, a room with a distance of 12 feet from the wall to the center will be roughly 452 square feet (12 x 12 x 3.14159). 

2. Convert Square Footage to BTUs 

Next, multiply the room’s square footage by 25 to get an idea of how many BTUs are required to cool down the room itself. So, a room that’s 196 square feet will need a mini-split unit with at least 4,900 BTUs. 

3. Repeat for All Interior Rooms 

To cool your entire home, you’ll need to determine the square footage of each room, then convert each to BTUs and add them together to calculate the right size mini-split for your needs.

Factors that Influence Mini-Split Size

Besides square footage, you’ll need to consider a few additional factors when weighing your options for mini-split air conditioning units. 

Ceiling Height 

The higher the ceilings, the more BTUs you’ll need to cool the space fully. If your ceilings are higher than the traditional 8 feet, you’ll need to increase the BTUs by about 20%. 

Climate 

Homes located in hotter regions will require more energy from a mini split to cool down the inside of your space properly. Homes in regions that experience temperatures hotter than 90 degrees for consecutive months will need units with about 30% more BTUs. 

Insulation

Older homes with minimal or ineffective insulation will also need mini-split options with higher BTUs. One way to make your AC more effective and maintain the cost of a smaller mini-split system is to replace your current insulation. 

Windows

The more windows in your space, the more energy will be required from your mini-split to heat or cool your home effectively, especially if the windows are old or in need of repair. Consider replacing your windows with energy-efficient models to improve heating and cooling capacity.

What to Do if You Have the Wrong Size Mini-Split

Maybe you mis-measured your space and purchased the wrong size mini-split unit. If you haven’t installed it yet, check the return policy with your HVAC company or the home improvement store to determine whether you can return or exchange it for the right size system. If the unit is already  installed, hire an HVAC expert to see if there’s a way they can adapt the unit to the requirements of your home.