Mini-splits are energy-efficient, ductless heat pump system that provide home heating and cooling. They are an ideal solution for homeowners looking for zoning options and strict climate control for individual areas.
They are a popular AC choice for homes with boiler, baseboard and wood-fired heat sources, as they do not require ductwork to install.
These systems are entirely electric. Now, if you’ve done a bit of research, you probably know that electric heat typically has a high operation cost. Much higher than gas-fired and wood-fired heat sources.
Since mini splits are electric, many people are afraid they will be expensive to run. It might surprise you, but they’re not. And there are a few big reasons why.
How Do Mini-Split Systems Work?
The Refrigeration Cycle in a Mini-Split
The basic concept of any mini-split system is the refrigeration cycle. These systems work via heat transfer, meaning they take heat from one area and move it to another.
This is the same way a central air conditioner works. The difference with heat pumps is they can run in reverse and provide heating as well.
Basically, this system works by absorbing heat with refrigerant and transporting it between the indoor and outdoor units.
Mini splits have a condenser that is located outside (just like a central air conditioner) and an indoor air handler (or head unit) that is located inside. These two units are connected to each other by copper lines so the refrigerant can flow between them.
When the mini split is running on cooling mode, the refrigerant absorbs heat from inside and expels it outside. On heating mode, it does the opposite. It finds heat in the ambient air outside and expels it through the indoor air handler.
Surprisingly, these systems can find heat in the air outside even when temperatures reach -15°F.
What Do Mini-Splits Require Electricity For?
Both the indoor and the outdoor units need power. The system won’t be able to run without it.
All furnaces and air conditioners use some electricity, even gas-fired ones. The only heating system that doesn’t use electricity in some capacity is a wood stove or fireplace.
Mini splits require electricity to power their computer boards, digital display, fans and the compressor.
The compressor will draw the most power. This component is located in the outdoor unit and is the heart of your HVAC system.
This is the part that pumps the refrigerant around between the two units. Without it, the system does not function.
If Mini Splits are Entirely Electric, How Can They Save Money?
While mini splits are electric systems, they are designed to be energy efficient and save on utility bills. But how is this possible?
For starters, mini splits don’t have to create heat like an electric furnace does. Electric furnaces and baseboards are so expensive because they need to “create” heat and distribute it throughout your home.
Mini splits use heat that is already available in the environment. They simply need to move it from one area to another.
The other big reason is that mini splits are fitted with their own smart technology that regulates their controls to maintain energy efficiency without sacrificing home comfort.
There are computer boards in both the indoor and outdoor units that are in constant communication with each other.
These systems also allow for zoning, meaning you can keep certain rooms cooler or warmer than others depending on your preferences. This means you don’t have to waste energy on unused spaces.
If used in conjunction with central HVAC systems or baseboard heating, you can use the mini split to take the strain off the other units. This is a good solution for homes with spaces that the central heater or AC can’t keep up with.
How Much Energy Do Mini-Splits Use?
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 capacity is measured in BTUs (British Thermal Unit).
A single BTU is defined as the amount of energy needed to raise the temperature of 1lb of liquid water by 1°F. This measurement is taken at the temperature water is most dense or around 39°F.
Mini-splits are sized in BTU per hour, which is often shortened to simply BTU in sales literature. Basically, larger home spaces need units with higher BTU capacity.
However, bigger isn’t always better. Your mini split needs to be sized correctly to maintain its energy efficiency.
If the unit is too small, it will run constantly as it tries to satisfy the thermostat.
If the unit is too large for the space, it will short cycle; meaning it will turn on and off all the time because it satisfies the thermostat too quickly and doesn’t adequately heat or cool the entire space.
Both of these issues will cause excess wear and tear on the system and will ultimately shorten its lifespan.
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.
That being said, if you don’t have experience in the field, you should really consider contacting an HVAC professional. It’s their job to size HVAC systems to homes and take into account all the factors that can affect BTU calculations.
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
|Cooling Load (Btu/h)
|Heating Load (Btu/h)
|7 (Very Cold)
Again, 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.
It’s good to be informed, but sizing HVAC equipment isn’t a DIY job. You can run into a lot of issues with improperly sized equipment and it will cost you in the long run.
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.
Mini splits can be a great, energy-efficient option for home heating and cooling. Don’t let the fact that they are electric scare you away.
They won’t have the operations costs of an electric furnace or other similarly expensive equipment.
While mini splits are an increasingly popular home HVAC choice, they aren’t suitable for every situation. If you are looking to heat and cool your entire home with a mini split, be sure to look into ducting options for bathrooms and closets.
And if you live in a cold climate, be sure to get a system that is rated for low temperatures. And when in doubt, call around to a few local HVAC companies and get their opinions for your home.
They will likely tell you that mini splits are easy to install and have low operations costs. But whether a mini split is right for you depends on several other factors.