Most people are familiar with window-mounted air conditioners and central HVAC systems. But they aren’t the only kinds of air conditioning systems available. When a central AC system doesn’t fit the bill, a mini split system can be a viable alternative.
What Is a Mini Split System?
A mini split is a kind of ductless heat pump. The system is made up of several mini splits that each provide heating and cooling to a single room or space in a home.
With central air conditioning and heating systems, one central unit manages a network of ducts that distributes air throughout a home or building. Some systems are zoned so airflow can be controlled independently in different rooms or zones.
Mini split systems are different altogether. Like zoned HVAC systems, they let you control temperatures independently in different rooms or areas. Unlike conventional central AC, which functions as one large unit that distributes air where it’s needed, a mini split is made up of several smaller units—typically one for each room or zone in the home.
Another major difference is that while central AC uses a duct network to move air around the home, mini splits are ductless heating and cooling. Each single mini split unit is an independent heat pump, with its own evaporator and condenser. In winter it draws in warm air from outdoors, then redistributes that air indoors. In summer it draws in warm indoor air and releases it outside.
Essentially, a mini split system is made up of several linked but independent ductless heat pumps. Each unit has its own thermostat and controls the temperature for the room in which it’s installed.
Best Ways to Use a Mini Split System
Heating and Cooling in a Small or Older Home
If your home is on the smaller side or is an older home, then it’s not always possible to install a duct system. In these homes, there’s often no room to install the network of ducts that a central AC system needs to operate. When this is the case, a mini split is a good alternative. Since no ductwork is needed, the system can fit into a home of any size.
Garage Conversion or Bonus Room
Expanding a central AC ducted network to include a newly built bonus room or a converted garage or attic space can be costly. The necessary remodeling work can be inconvenient too. Rather than going to all that trouble, it’s possible to install a single mini split unit instead. It’s much faster and less invasive. This strategy is especially useful for rooms that are split off from the main house, such as a studio or guest apartment in the backyard. In this case it’s impossible to extend the central system, making a mini split the best option.
Pros and Cons of Mini Split Systems
Pro: Easy to Install
Ductless mini split units are much easier to install than traditional HVAC systems. This is especially true if your home isn’t already set up for ductwork. Installing new ductwork is invasive because it requires getting into the spaces between walls and ceilings. This makes it potentially expensive too.
With a ductless mini split system, each indoor wall unit only needs a small two to three inch hole made to connect it to its respective outdoor units. It’s much less invasive, so it’s both easier and faster to install.
Pro: More Energy-Efficient
Ducts wear over time, developing cracks or separating at joints. This allows treated air to leak out of the system, wasting all the energy that went into heating or cooling. Leaking ductwork reduces the energy efficiency of your whole system and contributes to extra wear-and-tear damage too.
Ductless mini splits don’t have this problem. Each unit distributes air directly into the space in which it’s installed, meaning nothing is lost to leaking or broken ducts.
Pro: Built-In Zone Control
If you want to have a zoned central HVAC system, you need to install specific hardware, including electronically controlled dampers in the ductwork. That’s not the case with mini split systems. The zone control is built right in because these systems are made of independent units linked together. This makes mini splits highly flexible, without having to install extra components.
Pro: Reduced Heating and Cooling Costs
Because mini splits have built in zone control, you get individual control over the temperatures of different rooms or zones. This can potentially mean big electricity savings because you don’t have to waste energy on heating and cooling spaces that aren’t being used.
Con: Higher Upfront Costs
Depending on your system setup, you may pay more for a mini split than you would for a comparable central HVAC system. According to the Department of Energy, mini split systems typically cost around 30% more than comparable central systems. The amount you pay depends on several factors, including the number of mini split units you need and the size of the spaces you want to heat. You’re likely to save on energy costs in the long term, but it’s true that the upfront costs are often higher.
Con: Reduced Performance at Extreme Temperatures
Because mini split systems use heat pumps to generate heating and cooling power, they work best at moderate temperatures. They’re less efficient when temperatures get too hot or too cold. Below freezing level or above 95 to 100 degrees, they start to lose efficiency. This means the system may get more expensive to run on very hot or very cold days. It may also be less effective, not cooling the home as well as a central forced air system would do.
Con: Less Aesthetically Pleasing
Aesthetics aren’t everything, but for some homeowners, mini splits are a no-go because the wall-mounted indoor units are too obtrusive. With central cooling and heating systems, most of the machinery is hidden away in unused spaces. The AC air vents that feed air into each room are much less noticeable in contrast to large wall-mounted mini split heat pumps.
What to Consider When Installing a Mini Split System
How to Size a Mini Split System
The various mini split models available are sized according to the square footage of the space they can heat. This is measured in BTU, or British thermal units.
To determine what size mini split units you need, you first have to measure the spaces you want to heat. For each room where you want to install a mini split, measure the room’s length and width, then multiply the two to find the room’s square footage. The higher the square footage, the more BTUs the mini split unit should be. The conversion is roughly as follows:
- 150 to 250 square feet: 6,000 BTU
- 250 to 300 square feet: 7,000 BTU
- 300 to 350 square feet: 8,000 BTU
- 350 to 400 square feet: 9,000 BTU
- 400 to 450 square feet: 10,000 BTU
- 450 to 550 square feet: 12,000 BTU
- 550 to 700 square feet: 14,000 BTU
- 700 to 1000 square feet: 18,000 BTU
- 1,000 to 1,200 square feet: 21,000 BTU
- 1,200 to 1400 square feet: 23,000 BTU
This conversion depends on a few variables. If any of the following apply, more BTUs are needed per square foot:
- If temperatures regularly dip below freezing in winter or tops 95 to 100 degrees in summer
- In rooms where ceilings are higher than eight feet
- In spaces that are poorly insulated
If getting this right feels overwhelming, don’t worry! Reach out to CW Service Pros today, and one of our heating and cooling experts can make sure the measurements are done perfectly.
SEER Ratings
SEER stands for Seasonal Energy Efficiency Ratio. The SEER rating of an HVAC unit measures its energy efficiency via its relationship of BTUs produced to watt-hours of energy consumed. The higher the SEER rating, the more efficiently the unit uses energy to cool a room.
Because mini splits have better energy efficiency than central heating and cooling systems, they also have higher SEER ratings. When shopping for a new mini split unit, it’s easy to find options between 20 and 25 SEER. For forced air central AC systems, if you want a system over 20 SEER, your options are limited, as most are in the SEER 16 to 20 range and top out at SEER 21.
Changes to Minimum SEER Rating as of January 2023
SEER ratings were introduced in the 1990s. At that time all HVAC units had to have a minimum SEER rating of 10. Over the years, as HVAC technology has improved, minimum SEER ratings have increased.
As of January 1, 2023, minimum SEER rating increased again, to 14 in northern states and 15 in southern states. For residents of Texas, this means all new HVAC installations must, by law, have a SEER rating of at least 15. This includes mini splits as well as central AC systems. While it doesn’t apply to systems that are already installed, it will affect your heating and cooling options when you replace your existing system.
Call CW Service Pros for Mini Split Installation, Maintenance, and Repair
Not all homes can accommodate a central cooling and heating system. Fortunately, mini splits can be an effective alternative. Interested in learning more? Call CW Service Pros to talk to an HVAC expert about your options or to schedule an appointment.
