How Many Mini Splits Do I Need? (Zones & BTUs Explained)

Ductless mini-split systems offer effective and efficient cooling in one or multiple areas of your home.

They even provide greater temperature control than central air because each indoor unit works independently of the rest and can be set to different temperatures. This allows you to cool certain parts of your home without worrying about cooling everything at the same temperature.

Zone cooling with mini split systems also helps you decrease energy usage. With zone cooling, you can coll the parts of your home you are using without worrying about cooling your entire home.

If you’re considering a mini-split system for your home, it’s essential to know about the zones and how many you may need. In the guide below, we will discuss how many split ACs you will need for your home.

Air Conditioner Zoning Systems

Single Zone

Mini split air conditioners can be installed in what’s referred to as a single zone to cool just one area of your house. This is when one indoor unit responds to one outdoor compressor.

The outdoor compressor carries the refrigerant and power inside to the interior unit through a small pipe. The pipe is run through a small opening and is installed with minimal impact on your house.


Instead of a single zone in your house, you can have multiple zones that cool various areas. Instead of having just one indoor unit responding to the compressor, you can have up to five indoor units powered by one outdoor unit.

Each unit can be controlled separately using a remote control so you can program each unit according to your needs.

Mini Split Multi Zoning

Benefits of Multi-Zone Mini Split AC

You’ll Save Money on Energy Bills

Many people assume that a multi-zone colling system will increase their energy bill. But the opposite is actually true because they are designed to save you money. The United States Department of Energy has found that a multi-zone system can save you up to 30% on energy costs compared to a central AC system.These systems accomplish this because they allow you to regulate energy use in your home. You can ease the use of your system in rooms that are less frequented while keeping the rooms you are in comfortable.

They’re Easier On Your System

Have you ever stopped to think how much strain is put on the HVAC system in your home when it only has one zone? Instead of cooling the room you are in, it’s forced to control your entire house, even when sections of your house don’t need it.

When you use a mini split system, you only cool the areas that need it, reducing the strain on the system. This allows the system to work more efficiently and economically. And, less stress reduces the risk of damage that can leave you without an air conditioner in the middle of summer.

You Can Choose Your Zones

Ductless mini-split systems are astonishingly versatile, allowing you to create zones and provide separate environmental controls for each zone. You can have up to 8 zones per 1 outdoor unit which is more than enough for most households.

And if you have a lot of people living in your home, each with their own unique wants and needs, you can assign them each a different zone to their room. You can add zones when necessary with a mini split system, like if you build an addition to your home.

How Many Mini Splits Do I Need? General Rules of Thumb

One Air Handler Per Room

Instead of using one large blower, mini split air conditioners use multiple air handlers to push cold air directly into the room they serve. You’ll need a separate air handler for every room you want to be cooled.

You likely won’t need a separate mini split for smaller spaces like half bathrooms because your other mini splits should give them plenty of airflow.

Larger Room = Bigger Air Handlers

Mini split ductless air handler’s output is measured in BTUs. The bigger the room, the higher the BTU output you’ll need from the air handler. But you shouldn’t size your mini split based solely off of the square footage of your room. Several things can affect the BTU you need for your room, including:

  • Insulation levels
  • Number of windows
  • Number of light sources
  • Floor-type (carpet or hardwood)

The best way to size your mini split is to have a professional inspect your home and perform a load calculation.

Mini Split Remote Controller

Calculating the BTU’s For Cooling Multiple Rooms

Once you know how many rooms you need cooled, you need to find out how many BTUs, or British Thermal Units, you need. The larger the space you’re trying to cool, the more BTUs are required.

There is a BTU-to-room sizing rule of thumb for air conditioners that can provide a rough estimate of the mini split BTU per square footage you’ll need to efficiently service the room.

Square footageBTUs needed per hour

To get a general estimate of the proper mini-split sizing, you need to first determine the square foot of the rooms. For example, if your room is 30 feet long by 40 feet wide, it would be 30 x 40 = 1,200 square feet.

Now to get the approximate BTU rating, multiply the square footage of the room by 25. So, since your room is 1,200 square feet, you multiply 1,200 by 25 to get 30,000 BTUs.

You can use the calculation above for rooms that have a rectangular shape.

How To Create A Zoned Mini-Split System For Your Home

Once you have the size of the unit you need, you have to determine the type. Keep in mind, though, that the calculation above is for rectangular rooms. If you have a uniquely shaped room, you should speak to a professional about the size you’re going to need.

When you’re ready to choose your type, you can choose between a multi-port or a branch box.

Multi-port condensers are considered all-in-one. They can employ built-in refrigerant ports to make multiple connections from your outdoor compressor to the indoor units.

Branch boxes are a bit different. Higher capacity multi-zone condensers use a slightly more sophisticated system of connecting indoor units to the condenser using branch boxes.

A branch box will make a single connection to your outdoor condenser, supplying the right amount of condenser to multiple indoor units.

The final step is choosing your indoor unit. Several types of indoor units are available to serve your cooling needs. You can choose from:

  • Standard wall mount
  • Recessed ceiling cassette
  • Concealed duct
  • Ceiling cassette/suspended
  • Floor mounted

The indoor unit best for you will be based on your home’s layout and the aesthetic you are looking for. An HVAC professional can help you with this as well.

People Also Ask (FAQ)

How much does it cost an HVAC technician to install a multi-zone mini split?

The cost to install your multi-zone mini split will vary depending on the size of the rooms and how many zones you have. The national average to have a multi-zone system installed ranges from $3,150 and $9,000. Get a free local quote via the form below.

Do I need a permit to install ductless AC myself?

Local building codes will vary, but many will require specific permits to install certain HVAC products, including ductless systems. Before you start your project, check with your local codes department to ensure you’re in compliance before you start an installation.

Can a mini split cool a garage?

Mini split air conditioners are great ways to keep your garage cool in the summer. They are small and low-cost to operate, making them perfect for a small space like a garage. They also have high SEER ratings, making them ideal for garages.

Related Article Garage Air Conditioners


A mini-split system for your home is a great way to keep your home cool and save on energy costs. Ductless mini split systems allow you to cool separate zones independently, so you aren’t cooling parts of your home that don’t need it. Get started with your new mini split system today!

We’ve reviewed several brands of mini-split AC systems on other pages across our site.

You can read all about these other models in the links below.

Related Article – Senville Mini Splits

See Also – MR Cool Mini Splits

See Also – Gree Mini Splits

See Also – Daikin Mini Splits

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.