What Mini Split Size Do I Need? What Will It Look Like?

If you’re considering going ductless for your heating and cooling, then it’s time to start thinking about the mini split size you’ll need. Technically speaking, mini split sizing has to do with the strength of the system. But, you’ll want to know the physical sizes of the components are and how they’ll look in your home.


These are important questions, especially since you’ll have air handlers in quite a few rooms if you’re considering a multi-zone system. Fortunately, I have the expertise and experience to answer them.

I’ve worked for more than a decade as a product manager for Peirce Phelps, a nationwide HVAC distributor. My territory is the Mid-Atlantic states: Pennsylvania, New Jersey, Delaware and Connecticut.

Along with staying on top of all the latest models and innovations, I’m always working with hundreds of certified HVAC contractors who have installed thousands of ductless systems in the area.

In this article, I’ll go through sizing units based on heating and cooling needs, and the mini split dimensions for what gets installed in your home.

If you have more questions, use our dealer locator to find a certified installer near you. Our network of contractors have great reputations and years in service.


How to Size A Mini Split

There are three essential factors to consider when sizing a ductless mini-split HVAC system: BTUs, load calculation, and measuring the space.


BTUs, or British Thermal Units, are the most common unit of measurement for determining the heat output of an HVAC system. The larger the room, the more BTUs required to maintain a comfortable temperature. It’s a measure of the heat needed to raise the temperature of one pound of water by one degree Fahrenheit.

Load Calculation

Load calculation involves determining the amount of heating or cooling required for your space. It’s based on the square foot area of the room, the number of windows, the insulation, room layout, and other factors.

An experienced HVAC technician can perform a load calculation to determine the appropriate size mini split.

Measuring the Space

To determine the square footage of the room, measure the length and width of the room and multiply the two numbers.

Factoring in Layout

Rooms with high ceilings, large windows, or open floor plan usually need larger units to produce enough heating or cooling and circulate it.

General Sizing Guide

As a general rule of thumb, a 12,000 BTU air handler heats and cools a room size of 550 to 800 square feet. For open plan areas or large rooms with high ceilings, a 24,000 BTU mini split heating and air conditioner system can usually handle up to 1,5000 square feet.

However, you still need a professional load calculation to take all these factors into account. Undersized and oversized HVAC systems don’t work properly and break down due to extra wear and tear.

How Big Are Mini Splits?

The physical size of a mini split depends on the type of air handlers you choose and how many you’re installing.

Single-Zone and Multi-Zone Systems

Single-zone systems heat or cool a single room or area. That’s one outdoor heat pump and a single air handler inside. Multi-zone systems can heat or cool multiple rooms with an air handler in each zone.

Mini Split Dimensions And Parts

Mini splits consist of several parts, each with their own dimensions.

Air Handlers

Wall-mounted air handlers are the most common. They’re mounted high on a wall with average dimensions of 12x32x9 inches (tall, wide, deep).

Floor-mounted air handlers sit low on the wall, touching the floor. They look like radiators you see in hotel rooms. They’re usually 24x24x3 inches (tall, wide, deep).

Recessed ceiling cassettes are installed flush with the ceiling so there’s no sense of depth. They’re often 25×30 inches.

Heat Pumps

Heat pumps are the outdoor components. They’re boxes with a fan on the side. Most are around 24x32x12 inches tall, wide, and deep.

Larger units are twice as tall but still 32 inches wide and a foot deep.

Line Set Covers

Line Set covers are about the size of a rain gutter: around five inches wide and two inches deep.

Five Benefits of Mini Split Systems

If you’re still unsure of whether you want to go with a mini split to upgrade your home’s eating and air conditioning, here are five benefits to consider:

1. Exceptional Comfort

These systems provide consistent temperatures throughout your living space and stay within a degree of your thermostat settings. Regular forced-air setups can fluctuate by up to to 10 degrees.

2. Zoned HVAC

Ducted furnace and AC systems, mini split systems offer zoned heating and cooling. That means you can control the temperature of individual rooms or zones independently. You can set each room to a different temperature. Or, set them all the same and actually have even heating and cooling across the entire house.

3. Energy Efficiency

Mini splits use inverter technology to regulate the temperature. They can run almost constantly by slowing down or speeding up, instead of just turning on or off a few times an hour. The result is better temperature regulation but also much less energy use. It takes less power to run consistently than starting up over and over.

4. Versatility

Whether you need to cool a single room or your entire home, mini split systems can accommodate your needs. These systems come in various sizes, making it easy to find the right system to meet your specific requirements.

5. Quiet Operation

The indoor unit produces less than 25 decibels of noise which is about the same as leaves rusting or people whispering in a library.

Mini Split Sizing FAQs

If you have more specific questions, use the dealer locator to find a certified installer near you for a free, no-obligation consultation.


Is it ok to oversize a mini split?

Oversizing a mini split leads to inefficient operation and higher energy bills. The system will cycle on and off too often. It won’t produce enough heat or cooling and will wear out early. A professional load calculation takes square footage, insulation, window placement, and more into account.

Do mini splits use a lot of electricity?

Mini split use less electricity than other AC and heating systems, making them an energy-efficient alternative to traditional furnaces and central air. The electricity used depends on the system’s size, number of zones, and usage patterns. On average, expect 500-700 watts per hour for single zone units. 

Let us help you find the right mini split installer for your home in Lancaster, PA or anywhere in Pennsylvania, New Jersey, Maryland, and Delaware.