Mini-split systems are a fantastic way to provide heating and cooling for your home. They are very efficient and dependable, making them a solid choice for many people.
But since the global energy crisis hit the news, we’ve been getting a lot of questions about whether they are expensive to run.
The price of electricity was on the rise anyway, but the war in Ukraine pushed prices even higher. So, it’s hardly surprising that people looking to install a mini-split system are concerned about running costs.
This article looks at the factors that affect a mini-split‘s running costs. Being aware of these will help you keep bills as low as possible.
We’ve also included a real-life example of running costs for a mini-split heat pump over a six-year period, which is long enough to smooth out unusually cold or warm years and reflect the actual cost.
How Much Energy Do Mini-Split Systems Use?
Mini-splits use electricity to keep a home’s temperature comfortable. Overall, they are efficient HVAC systems and don’t use much energy, keeping running costs low. Though there are many factors to consider, running a mini-split instead of a central ducted HVAC can save up to half or more on your bill.
Again, this is a rough estimate, and many variables will affect the cost, including location, insulation, usage, and function of your system.
Before we look into the factors influencing a mini-split’s energy use, let’s grasp what that energy is used for and how these systems function.
How Do Mini-Split Systems Work?
Having a mental model of how any machine operates helps understand specific concepts like the variation in energy consumption under different conditions.
So, let’s consider a mini-split system and remove the mystique that surrounds how it does its job.
The Refrigeration Cycle in a Mini-Split
The basic concept of any mini-split system is the refrigeration cycle. That’s what it uses to move heat from one place to another.
In the case of air conditioning, it moves the excess heat from your living space to the outside environment. A mini-split in heating mode does the same thing but in reverse— it collects heat from the air outside your home, moves it inside, and blows it into your living area.
A clever French physicist named Sadi Carnot first put forth the thermodynamic concepts underpinning the refrigeration cycle in 1824, so we’ve known about them for a long time. We have more recently started applying them to heating and cooling our homes.
The second law of thermodynamics states that heat cannot spontaneously flow from a colder place to a hotter location. Unless that is, work is done to make the heat move.
A helpful analogy here is that of a ball, which cannot roll uphill unless kicked. The kicker imparts energy to the ball, making it travel uphill.
Similarly, the heat pump mini-split system provides the impetus (in the language of our ball analogy, the kick) to move the heat from a colder location to a hotter one.
It uses electrical energy to operate a compressor, which concentrates the heat in the refrigerant fluid that flows around the system and increases its pressure before passing it to the condenser. Then, it releases heat via the condenser coils on the warm side of the system.
The refrigerant then continues its journey through an expansion valve into the evaporator (on the cold side of the system). It once again collects heat from the air before beginning the cycle all over again.
In the case of an air conditioner, the air handler blows air across the evaporator coils and into the room, creating a cooling effect. A mini-split in heating mode blows air across the condenser to warm it up before using it to heat the living space.
In addition to air-source heat pumps, some heat pumps collect heat from the ground or water. You can read more about the different types of heat pumps in our article here.
What Do Mini-Splits Require Electricity For?
Mini-splits use electricity to move heat from the cold side of the system to the hot side, but which components need the most?
The component that uses by far the most energy is the compressor. This component compresses the refrigerant gas into liquid form and pumps it into the condenser coils, where heat is released.
The pressure we’re talking about here is between 200 and 300 psi, which is ten times higher than a car tire. That takes a lot of energy!
The compressor will draw around seven amps as it performs this task.
The subsequent most considerable energy consumption is from the fans that blow air across the condenser and the evaporator. These typically run at between 1.5-3 amps.
How Much Energy Do Mini-Splits Use?
We now know that most of the electricity needed by mini-splits is used to run the compressor and fans. But how much energy do they consume in a typical setup?
The amount of energy a mini-split uses is proportional to the heating and cooling load it is designed to cope with.
Heating and cooling load are measured in BTU, which stands for British Thermal Unit and was developed to compare different sources of energy using an equal basis.
A single BTU is defined as the amount of energy needed to raise the temperature of 1lb of liquid water from 39°F to 40°F (39°F being the temperature at which water is most dense). This energy is about the same amount that you get from burning a match, so not much!
To put this in terms of gas for your vehicle, one gallon of gasoline provides 120,286 BTU or the same as 120,000 matches.
Mini-splits are sized in BTU per hour, which is often shortened to simply BTU in sales literature. The higher the HVAC load, the more BTU required and the bigger the unit you need to install.
So, that’s how HVAC demand is measured, but how do you know what you need for your home?
Factors Affecting Mini-Splits’ Energy Use
Specific energy expenditure of a mini-split depends on several factors, including:
- Floor area of the building
- Height of the ceilings
- Climate zone where the building is located
- Wind conditions
- Insulation of the building
- Solar gain from windows
- Amount of heat generated by people, cooking, and electrical appliances
- How airtight the building is
- Quality of windows (e.g. double or triple glazed)
There are other factors, of course, which illustrate that running costs will be different according to your specific requirements, so take any figures with a grain of salt and make sure to get professional advice before committing to a decision.
How to Calculate the HVAC Load of Your Home
Of course, you could do all the calculations yourself, but that is quite complex and beyond the scope of this article.
If you want to get a ballpark estimate for your home’s heating and cooling load before speaking with a professional, the best thing to do is to use an online calculator such as this one.
A good calculator will account for most factors listed above and make sensible assumptions to ensure the information is reasonably accurate.
Energy Consumption Examples for Mini-Splits
Using the calculator above with its default assumptions, we calculated the heating and cooling loads estimates for a 330 sq ft room in some example states. We took a spread of locations across the country to illustrate what typical loads are likely to be in each of the different climate zones.
The examples below assume the house was built after the year 2000. They also imply two exposed walls with two or three two-pane windows, excellent insulation, a ceiling height of 8ft, and the characteristics of a 330 square feet living room.
Example HVAC Loads for a 330 ft2 Room (For Illustration Only)
|Building America Climate Zone||Location||State||Cooling Load (Btu/h)||Heating Load (Btu/h)|
|4 (Mixed-Dry)||San Andreas||California||3,800||3,700|
|7 (Very Cold)||Juneau||Alaska||2,300||5,000|
Always have a qualified professional do your heating and cooling load calculations. There are many variables, and your specific needs are likely different from another.
How Much Does It Cost to Operate a Mini-Split?
We can estimate the cost of running a mini-split based on the heating and cooling loads, the efficiency of the unit, and the cost of electricity.
Example Cost of Cooling Using a Mini-Split
For illustrative purposes, let’s assume that we have a mini-split cooling our home in Tallahassee, Florida. The estimated cooling load we obtained from the calculator above is 5,000 BTU/h.
We can assume that the unit operates for eight hours a day for 125 days during the cooling season. That gives us a total of 1,000 hours of operation during the season (8 x 125).
The efficiency of mini-splits is measured using something called a SEER rating. SEER stands for ‘seasonal energy efficiency rating’ and is the unit’s cooling output during a typical cooling season divided by the total electric energy input during the same period.
A typical SEER rating for a unit like this would be 20. Although higher is possible with modern units, these would be more expensive.
The cooling load from our table above is 5,000 BTU/h, so 5,000 x 1000 hours = 5,000,000 BTU for the whole cooling season.
With a SEER of 20 Btu/Wh, the electrical energy used would be 5,000,000 ÷ 20 = 250,000 Wh = 250 kWh.
Assuming the price of electricity is 0.11 $/kWh, the cost of running the unit during the cooling season would be 250 x 0.11 = $27.50.
Remember, this example is for a single 330 ft2 room with excellent insulation, so if you want to cool a larger room or a whole house, or if your home is less well-insulated, it will cost more than that. However, this is a helpful illustration of the affordability of these systems.
For more information on insulating your home, please read our article on Energy Star & ZERH Homes, which covers different insulation needs.
Are Mini-Splits Expensive to Run in Heating Mode?
Homeowners can do a similar calculation for mini-splits in heating mode, but instead of SEER, the ‘heating seasonal performance factor’ (HSPF) is used.
Rather than bore you with more math, let’s hear from someone who has run his heat pump for six years and has gathered data to show how well it has performed.
Mini-Split Heat Pump in Michigan
Matt Rosendaul installed a mini-split heat pump system in his home in Michiana in 2014.
Before he left for North Carolina after selling his house, Matt posted a video explaining the system he has been operating since 2014 and discussed a couple of minor service issues dealt with under warranty.
Matt lives in the middle of Michigan, where the temperatures often get down to 20°F or so, which is very cold. However, there is still enough heat outside for the heat pump to collect and use to keep the house warm.
The system “works fantastic and has saved us a lot of money,” said Matt.
According to the manufacturer, Matt’s mini-split system should operate well down to 15°F, but he says that in his practical experience, it actually functions satisfactorily down to about 9°F. He could have bought one that operates down to -15°F, but that would have cost more, and he has kept his propane gas boiler, which can keep the house warm during a frigid spell.
Matt’s home is very airtight and energy-efficient, which you should bear in mind when you read the operating costs of his mini-split.
He also has a long, narrow house that lends itself well to the ductless heat pump, which blows air into the living room and continues down the house to warm the bedrooms. They are a few degrees cooler than the living room, but that is fine for him.
Matt’s house needed an estimated 20,000 BTU to meet his requirements. He emphasizes the need to have an HVAC contractor do the calculations because there are so many variables to consider.
He bought a 19,500 BTU unit that, “seems to be working great for us.”
However, the most interesting part of the video was the section where he talked about the cost of running the system.
Are Mini-Splits More Expensive to Run Than a Propane Boiler?
If heating the house using just his propane boiler, Matt’s boiler uses $12 per month of electricity to run the pumps and 650 gallons of propane gas. In total, this costs $1,300 per heating season.
Running just the mini-split for heating uses $57 of electricity per month or $342 per heating season.
This operation saved $5,748 over the six years since the system has been functional—and he only paid $4,100 for it to be installed. So that means he’s up $1,648. We would call that a win!
You can watch Matt’s video here.
Final Word on Mini-Split Energy Usage
Mini-split systems are highly energy-efficient, and the technology and efficiency keep improving.
They are not expensive to run and can provide heating and cooling for homes in all climate regions in the US, even comfortably heating houses such as Matt’s in central Michigan.
Many variables affect the HVAC load of your home, and it’s crucial to get a qualified contractor to design your system to ensure it has the appropriate capacity.
For a very rough guide, you can use one of the many online calculators, which give indicative figures for HVAC loads in each climate zone. They can also give you an idea of costs, which is helpful in the early stages of a project, but take these with a grain of salt and get specific advice before going ahead.