Air Source Heat Pump vs Mini-Split (Explained & Compared)

When choosing a heating and cooling system for a home, going with the most efficient option possible is often high on the agenda.

Whether a home has existing ductwork or not, different air source heat pump systems are available to serve these varying home HVAC setups.

Mini-splits and air source heat pumps are some of the popular options available to households, but what is the difference between the two?

Standard air source heat pumps are units typically designed for use with ductwork to help heat a whole house, while mini-splits are a type of ductless air source heat pump that can serve one or more rooms using one or more indoor air handling units.

Our own air source heat pump is a ductless system, but it’s an air to water heat pump system rather than an air to air.

Air Source Heat Pump Pipe
The pipes behind our own air source heat pump as part of a ductless system

Both standard air source heat pumps and mini-split systems can offer the same sustainable way to help heat and cool a home, and both have their pros and cons.

We go over in more detail below:

  • The differences between standard air source heat pumps and mini split systems
  • The pros and cons of each
  • Choosing between a mini split and a standard air source heat pump

Air Source Heat Pumps Explained

An air source heat pump is an outdoor unit that absorbs heat from the outside air.

For example, our own external air source heat pump unit is shown below. It uses fans to force air over refrigerant flowing through a coil to be able to extract heat energy from the air.

Air Source Heat Pump

The absorbed hot air is transferred directly into a home for use indoors as heating.

Depending on the type of system being used, air to air or air to water, heat is provided through blown hot air for space heating (air to air) or through a central heating system to a radiator, underfloor, or hot water heating system (air to water).

As we have an air to water system, our external air source heat pump unit transfers heat into our home using refrigerant in pipes.

Air Source Heat Pump Pipe

This heat is then used within a water-based central heating system that utilizes underfloor heating and radiators to release the heat. Our heat pump also provides us with domestic hot water and so we have a hot water tank to store and deliver hot water to taps etc.

Air Source Heat Pump Hot Water Tank

Air to water heat pump systems can be more common in milder climates (such in the UK where we live) because using a heat pump for cooling purposes isn’t such a necessity.

We have separate air conditioning units that serve individual rooms and don’t use our heat pump for cooling purposes.

Air Source Heat Pump & Air Conditioner
Our air conditioning unit (left) and air source heat pump (right)

On the other hand, air to air heat pump systems work with an air-based heating system inside a home.

This can include both ducted and ductless air space heating systems.

Ducted means the use of ducts to move hot or cool air around a home.

Ductless means the use of a pipework to move heat from one appliance to another, such as from an external air source heat pump unit to an indoor air handler unit, and vice versa. The indoor unit then provides heated air at a specific location in a home.

See our articles comparing air source heat pumps and air conditioning, and comparing ductless and ducted heat pump systems for more information.

Air Source Heat Pumps vs Mini-Splits Compared

The term ‘air source heat pump’ can refer to all forms of appliances that utilize an external unit to extract heat from the outside air.

This can include mini-split units.

However, for the purposes of this article we refer to standard ducted air source heat pumps as air source heat pumps, and ductless systems as mini-splits.

Standard air to air heat pumps can, depending on where you live, be the most common type of air source heat pump system, and uses ducts to provide heating and cooling around a home.

These air source heat pump systems are ducted systems and are therefore whole-house heating and cooling setups.

Most air to air heat pump systems are split systems, where the two separate coils (the heat exchangers) are located indoors and outdoors. A centralized blower pushes warm or cool air around a property through ductwork.

A standard air source heat pump can also be a packaged system where both coils are located outside and an outdoor fan pushes air throughout a home, again through the use of ducts.

Mini-splits are a type of air-source heat pump which don’t require any ducts to provide heating or cooling for a home.

Mini-splits are therefore ductless systems and can often be referred to as ductless mini-split systems.

This system comprises a single outdoor condenser or compressor and one or more indoor air handling units.

Mini split (left) and air conditioning unit (right)

The indoor units are typically suspended from the ceiling or mounted high on the wall to send the hot air downwards into the space. Instead of a convoluted duct system, the system features refrigerant line connections from the indoor units to the outdoor compressor. Other connections can include suction tubing, a condensate drain line, and a power cable.

An air handling unit can be found as part of a ductless mini-split system

As a result, mini-splits only provide heating and cooling at the location of indoor unit and so can be less effective as whole-house systems.

However, multiple indoor air handling units can typically be connected to a single outdoor mini-split system unit, meaning that a whole-house could be served if the setup is right.

Ductless mini-split systems can therefore be a better choice for when it’s not feasible to install ductwork, or to extent existing ducts. They can also be more feasible for smaller sized properties that don’t require a large network of ducts, or where a home is more open-plan.

You can control the various indoor air handling units connected to the single compressor independently, but they all rely on one outdoor heat pump unit to dispense or absorb heat.

Pros & Cons of Ductless Mini Splits

The Advantages of Mini-Splits

Increased Efficiency

The technical specification of most mini-split heating systems means they consume a small amount of energy while working. The result is a Seasonal Energy Efficiency Ratio (SEER) potentially delivering up to a 40% reduction in your energy bills.

The units can also feature variable-speed compressors, which only run at the optimal speed needed to deliver the right amount of heat in any space. Many other heating systems feature one or two-speed solutions, and thus they have to cycle on and off a lot while working.

Easier Heating Management

You’ll likely want to heat more than just your bedroom and living room. Any sunrooms, basement, and attic are other places where you may want your heating to reach, too. Mini-splits ensure you can have as many indoor units as you want to keep your home at desired temperatures.

Since you can control each “split” individually, you don’t have to worry about wasted heating in unoccupied spaces. The design of these systems allows you to keep the units in some rooms working while others elsewhere are off.

The enhanced heating management adds to the efficiency of these units. You can help rack up sizable savings on energy bills if you only heat or cool a small portion of the home instead of the entire space.

Easier Installation and Management

Mini-split units are ductless solutions that come in handy when installing ductwork for your heating and cooling is impractical.

Ductwork in homes is useful for a variety of reasons. However, the modifications, maintenance, and cleaning required to make it work can be a hassle.

Choosing a mini-split unit is a sure way to avoid the downsides of duct-based heating and cooling without missing out too much on the upsides.

Improved Flexibility

The ductless nature of mini-split systems makes them a super flexible heating and cooling solution.

They can allow you to control the temperature in individual spaces, but another element of their flexibility is in how they can work in tandem with central heating and cooling systems.

You can use mini-split units in areas of your house that are out of the reach of a standard central unit. Many installers recommend this combination for large homes.

The Disadvantages of Mini-Splits

Weaker Filtration Systems

Mini-splits feature air filters, but they can be seldom powerful enough compared to the filters on ducted systems. They’re less equipped to rid your home of dust, odors, and allergens. 

You can bypass this problem by adding carbon inserts to the units, but these have to be replaced regularly. The replacement can become a hassle depending on your environmental conditions. You may also use air purifiers, but these also increase the overall cost of running your units a bit further.

Dampened Aesthetic Appeal

Mini-splits have a line to house for the electrical connectors, the condensate drainage, etc., which has to go from the indoor unit to the outdoor unit. If you have multiple indoor units in different corners of your home, the result could be unsightly lines running down the sides or corners of your home.

It detracts from your home’s appearance as these lines are immediately visible to anyone looking. You can mask the lines with PVC or so-called “line hides,” but even those also pose a problem of their own. They also bump up the installation cost a little, so many installers choose to ignore them.

Condensate Drainage Problems

Mini-split systems collect moisture in the condensate line. In most cases, the accumulated moisture can find its way to a drain outside due to gravity. However, this isn’t always the case.

If the condensate isn’t flowing away as it should, you’ll need to install a condensate pump. This ensures the moisture isn’t percolating indoors for long periods. Unfortunately, installing a condensate pump adds to the installation cost. Not to mention, they can be noisy and a maintenance headache.

Maintenance Demands

All HVAC units, including mini-split systems, require regular maintenance to ensure optimum function, maintain efficiency, and ensure the system lives out its lifespan.

Multi-split systems are more demanding in this regard as the filters need to be cleaned regularly. Since these units can provide heating and cooling, they’re typically used all year round. In this scenario, you have to clean the filters every couple of weeks. If you only use the system in one season (perhaps only in the winter), you can clean it 2-3 times over the season and allow it to sit for the rest of the year.

Higher Upfront Costs

Compared to other solutions, you may need to shell out a bit more in upfront costs to install mini-splits. Of course, with the possible higher efficiency, you may recoup the costs faster compared to other options.

Still, you have to consider the overall cost, especially when you already have ductwork in your home, because you may benefit from installing a central air source heat pump instead.

Pros & Cons of Ducted Air Source Heat Pumps

The Advantages of Ducted Air Source Heat Pumps

Lower Upfront Costs

Choosing an air source heat pump can be a cheaper option to go with if your home already has existing ductwork that won’t require any modifications.

Most high-efficiency units also have SEER ratings of around 20, so you can recoup your expenditure in good time. Other factors may contribute to a higher cost, but overall, you can pay a smaller sum compared to a mini-split solution.

Better Heating and Cooling Consistency

A central air source heat pump properly sized for a home with ductwork can deliver more consistent heating and cooling than ductless solutions like mini-split units.

The consistency achievable with a central unit can only be matched with a ductless system if you install multiple indoor units or heads. Even then, you may still feel some difference in the overall feel of the heating and cooling.

Easier Integration With Air Filtration Systems

Fitting a central air source heat pump with air filtration systems is straightforward—even more so when your home has ductwork.

There are many whole-home air quality solutions for ducted ASHP setups. Dehumidifiers, humidifiers, and air purifiers can work better with a single unit compared to the multiple heads in a mini-split.

Options like a dehumidifier can also help reduce the workload on your HVAC system, improving its efficiency and ensuring longevity.

Better Product Variety

If you’re in the market for a central air source heat pump, you’re sure to find a myriad of options to choose from. Unfortunately, this isn’t the case for other solutions such as mini-splits. The difference between high-quality units may not be striking, but it’s nice to have options. Competition brings lower prices, better warranties, etc.

The Disadvantages of Air Source Heat Pumps

Higher Energy Bills

Single-unit air source heat pumps have to run at full tilt most of the time to heat or cool the entire home. The approach invariably leads to energy wastage as rooms with no occupants will get cool or warm.

An efficient, modern air source heat pump cab reduce your bills compared to more archaic systems. In fact, switching to an air source heat pump can save you $459 per year, but in any comparison with mini-splits, a single-unit system may lose.

Poor Zone and Temperature Management

Single-unit air source heat pumps don’t allow granular control—contributing to the higher energy bills mentioned above.

If you have multiple rooms in your home, you can’t vary or turn off the heating and cooling depending on what you need. You can’t turn off the heating for specific rooms either. Of course, it’s not a disadvantage if all the rooms are busy most of the time. Still, occupants will appreciate having better control of the heating and cooling.

Maintenance Work Required

You have to clean and maintain your ductwork regularly to prevent expensive repairs. The yearly maintenance cost can be sizable, as you’ll typically need to hire a professional to clean and maintain the duct.

Talk to your HVAC installer for proper guidance on maintaining your ductwork and keeping it working effectively.

Choosing Between An Air Source Heat Pump and Mini Split

The right choice will vary from one home to another. If you already have ductwork, choosing a standard air-source heat pump looks like a straightforward choice.

However, if you have a large property with a few vacant rooms, a mini-split solution may be more efficient overall.

You may also choose to install both solutions. A central air source heat pump can serve most of the home, while some mini-split units can serve parts without ductwork and areas that are tougher to heat or cool.

Air Source Heat Pump vs Mini-Split

If you want the best indoor climate while reducing your energy bills, you have to carefully weigh your options when choosing an HVAC system. In the choice between a standard air-source heat pump and a mini-split, it’s all about juxtaposing your unique needs against your existing heating and cooling infrastructure.

The comparison above should give you a clearer picture of what to expect from both solutions and which may be better for you. But if you’re still unsure, consider talking to a certified HVAC installer.

Further Reading

Air to Air and Air to Water Heat Pumps Explained

Parts Of An Air Source Heat Pump System Explained

How An Air Source Heat Pump Works

Pros & Cons Of Air Source Heat Pumps

Air Source Heat Pump Air Handling Units Explained

Air Source Heat Pumps & Underfloor Heating