Understanding Mini Split Systems Pros & Cons

Mini-Split Systems Pros & Cons

What’s the Divide on Mini Splits?

Most people today are conscious of the need for their HVAC (Heating, Ventilation and Air Conditioning) systems to run as energy efficiently as possible, if for no other reason than it saves money on their utility bills, not to mention it’s better for the environment.

If you’re building a new house or looking to replace your existing HVAC, you might want to consider a mini split system. While these systems have been popular in Europe for some time, mini split systems are becoming a more popular application here in the U.S. and particularly in energy conservation-minded California. 

Mini split systems are not ideal for every homeowner or commercial business, however. To understand more, let’s take a look at:

  • How mini split systems work
  • Pros of mini split system
  • Cons of mini split systems
  • Top manufacturer of mini split systems

How a Mini Split System Works

A traditional HVAC system employs ductwork to circulate conditioned air throughout your house. Most mini split systems don’t use ductwork at all (there are some newer models that utilize ductwork for their air delivery system, these are for specific scenarios).

Like a traditional HVAC system, there is an outside unit and a single indoor unit that distributes that conditioned air. Hence the term, “split-system.” 

A mini split system also has two split units, an outdoor heat pump or condenser and an indoor air handler or handlers.. Since the indoor component comprises multiple mini units, one for each room or zone, it’s a “mini split.”

A mini split system may be used for air conditioning only, or both heating and cooling. The outside units of AC-only mini split systems employ a condenser with refrigerant to cool air until it transfers into a liquid. The cold liquid runs through copper lines to the individual units that cool the air in the zoned room.

In the case of a heating and cooling mini split system, the outside unit is a heat pump that transfers thermal energy to heat or cool. The same refrigerant used to cool warmer outside air is also used to extract heat from colder outside air and conduct it through copper tubes to the zoned rooms (we know, it’s kind of hard to wrap your head around how something called a refrigerant can make heat; it involves the Second Law of Thermodynamics, which gets a bit technical. Just trust us, that’s how it works).

Pros of Mini Split Systems

The benefits of mini split systems include:

Energy Efficient Zoning

Mini splits have some of the highest efficiency rate systems on the market and are anywhere from 25 to 35 percent more efficient for two reasons:

  1. No ductwork. So there’s no energy loss (up to 25 percent) to conditioned air as it moves through the ductwork.
  2. Inverter-driven compressors speed up and slow down based on the needs of the system instead of shutting off entirely, and thus require more energy to start up again, as does a traditional HVAC compressor.

In addition, mini splits have the capability to maintain up to 8 indoor zones to one outdoor heat pump. This allows everyone in your home to control their own climate. Most importantly, you won’t be heating or cooling the entire home just to achieve comfort levels in one room.

Here is the bottom line: the more energy efficient your heating and cooling, the lower your overall energy bill. 

No Ductwork, No Problem

Have we mentioned that mini split systems don’t need ductwork to work? (Fair warning: we’re going to mention it again a few times, it’s a key feature.) 

The fact that they have no ductwork means they are a great solution for home retrofits or additions. If you’re looking to add air conditioning to an existing furnace, a mini split system could be an alternative option to consider. 

There is no need to break through walls and crawl through tight spaces to add runs to the ductwork. All you need is a hole about three inches in diameter to run conduit linking the indoor and outdoor units; the conduit contains the power and communication cables, copper tubing, and a condensation drain line linking the outdoor and indoor units. 

An added benefit to no ductwork is simpler maintenance – no ducts to periodically reseal, no ductwork that can get clogged with debris to the point where it needs to be cleaned.

Easy to Install

Since there’s no ductwork that requires altering existing construction, mini split systems are relatively easy to install. Not so easy though that it could be considered a DIY project for most homeowners. 

But since it is an easier installation for your HVAC technician, it is less intrusive than a traditional split system. In addition, some mini split systems have an auto-dry function that sucks up moisture from its coils, so you also have to some degree an automatic maintenance that can save you money spent on service calls.

Quieter Operation

Mini split systems have some of the lowest decibel ratings on the market, usually expressed as dB (A) for noise levels detectable to the human ear. The indoor units of Mitsubishi Electric mini splits, for example, operate as low as 19 dB (A), which is quieter than a human whisper. The outdoor units operate at about 58 dB (A), the level of sound found in a restaurant.

A Better Alternative to Window AC Units

If you’re just looking to add air conditioning to a room, a mini split has a number of advantages over a window air conditioner. Some of the cons of AC units can include:

  • Noise level
  • Expensive to operate
  • Unattractive design 
  • Limits outside light by blocking a large portion of the window

If You Use Solar

The sun isn’t always out. No matter how many solar panels you have, if there are enough dark and rainy days you are forced to resort to battery back-up. Mini split system energy efficiency particularly comes in handy when you are running on batteries. 

Mini split systems have some of the best results on the market when working together with solar systems and battery backups. Because they use a variable speed compressor that allows both indoor and outdoor units to run as low as 15 percent capacity, they have some of the lowest-rated running amp draws. 

This means less amp draw on your solar system as well as on your battery back up during our PSPS (Public Safety Power Shutoff) times. They also have extremely low amp draw during start up which is crucial for both solar battery backup systems and generator systems.

Variety of Indoor Units and Controls 

You may have seen pictures of a mini split system that shows a high wall mount unit located centrally in a room. Not the best look. However, there is a sleek designer series that comes in black, white or silver. 

Nor are you limited to wall mounts. There are two types of cassette units, one directional and the other multi-directional, that are flush mounted to the ceiling. An additional choice is a low wall mount unit that sits on the floor level of a wall. 

The latest innovation is a ducted system that can be installed in your closet, garage, crawl space or attic using the same ductwork of a conventional HVAC system. This is an ideal application if you want to zone off a room that is used infrequently. 

Another option is adding onto a house or building where the existing HVAC system is undersized to accommodate the addition but is otherwise in good working condition. Why pay to replace the entire system when a multi-split is much more economical.

You can even mix and match indoor units to accommodate room decor and different personal preferences. On top of that, there are a variety of control options: wired or wireless wall-mounted, a handheld and even a smartphone app.

Don’t Fear the Heat Pump

Some people are reluctant to use heat pumps because they fear they won’t produce 100 percent heating capacity once temperatures reach near or below freezing. Mini split systems have to utilize heat pumps to have the capability to heat and cool, so this can cause some concern.

This is specifically why Mitsubishi Electric developed its Hyper Heating Inverter® (H2i®) technology. These systems provide 100%  heating capabilities down to -5 degrees fahrenheit. So you will be comfortable on the coldest winter morning.

Cons of Mini Split Systems

The disadvantages of mini split systems include:


Despite the variety of indoor units, some people just don’t like the idea of a visible unit in a room. While the outdoor models have a slim line look with a smaller footprint than the conventional heat pump or air conditioner,  indoor wall mounted units can feel intrusive. In some cases homeowners can go with the ducted models or flush mount ceiling cassette units that are somewhat less aesthetically offensive.


Generally speaking, the upfront cost to install a mini split system is a bit more than a conventional system. This is due to the technology used and installation time required. However, what you pay in upfront cost provides you with a higher and quicker ROI through efficiency and zoning capabilities.

Lack of Familiarity

Because mini splits are newer to our service area, it can take Ongaro and Sons’ customers a bit of time to learn how to use the system and get used to the controls and thermostats.   These systems are designed to be “on” all the time, which can take some getting used to. This allows the system to provide consistent comfort. 

Also, the temperature coming out of the vents in heat mode, just like all heat pump systems, will not be as warm if you are used to old gas furnaces, especially if the old system was 80 percent or less efficient.

Ongaro and Sons Is a Mitsubishi Elite Premier Diamond Contractor

So you may have noticed there are more pros than cons. We at Ongaro and Sons feel that a mini split system is a good choice for the right application. Our technicians have completed extensive mini split training and have technical skills and product knowledge that has allowed them to become the only Elite Premier Diamond Contractor for Mitsubishi in the Northern Bay.

Mitsubishi is the number one manufacturer of mini split HVACs for residential and commercial applications in the U.S. Because we have earned a coveted contractor position with this outstanding company, Ongaro and Sons can offer our customers a full 12-year parts and labor warranty on Mitsubishi mini split systems.

Why choose a Mitsubishi multi-split system? Mitsubishi has the highest rated SEER (Seasonal Energy Efficiency Rating) systems on the market, achieving 26+ SEER. Even their ducted systems achieve higher than most conventional systems in efficiency ratings.

Mitsubishi units also have the lowest decibel ratings on the market, as low as 32 decibels for outside units and 19 decibels indoors. It’s one of many reasons why we here at Ongaro and Sons like to shout Mitsibushi’s praises.