Mini-splits are touted as an efficient way to heat and cool your home, saving you money on utility bills. With energy prices rising, many of us are looking for ways to save money on heating and cooling.
The efficient use of energy is also a concern from an environmental point of view, and many of us are keen to play our part in mitigating the worst effects of climate change by minimizing our carbon footprints.
So, there are compelling reasons to make the switch to mini-split systems. But how much of a difference do they make, and how much electricity do they use?
Mini-splits use far less energy than equivalent electrical resistance heating systems. Still, you might be wondering how they achieve this and what you can expect to pay in terms of electricity for a typical installation.
We’ll cover that in the rest of this article, so keep reading to find out.
For more information on energy efficiency in the home, please read our article on how to save energy with affordable tools.
How Much Electricity Do Mini-Split Heat Pumps Use?
A mini-split’s electricity consumption depends on your home’s heating and cooling load, which is affected by outside temperature, level of insulation, and other factors. But, an average-sized apartment might require a 12,000 Btu unit, which could use about 10 kWh ($1.45) of electricity per day.
Now let’s make sure you’re clear on what a mini-split is.
What is a Mini-Split Heat Pump?
A mini-split is a piece of heating and cooling equipment permanently installed in your home and comprises two main elements—an outdoor unit and one or more indoor units.
The system leverages the refrigeration cycle to collect heat from outside the building in refrigerant fluid and distribute the accumulated heat inside the building.
After collecting heat from the outside air, the refrigerant passes along a copper pipe, called a “line set,” connected to the indoor unit.
Upon reaching the indoor unit, the refrigerant flows through a coil, where the air is blown across it. Next, the refrigerant heat passes through the copper coil’s wall and heats the air before it is blown back into the room.
The warm air circulates throughout the room and provides a heating effect to maintain a comfortable temperature. In cooling mode, the process operates in reverse, with the heat being collected from the room and emitted from the outdoor unit coil.
In mini-splits, heat is moved from one place to another, which is far more efficient than generating heat directly. This is one of the reasons that the system uses less electricity to generate the same amount of heat as an electrical resistance heater.
Factors Affecting The Electricity Usage a Mini-Split
The electricity a mini-split uses depends on various factors, including:
- The difference between the outside and inside temperatures – the more significant the difference, the harder the unit must work to maintain a comfortable indoor temperature.
- The size of your home – more electricity is required to heat a larger space.
- How well insulated your home is – better insulation results in lower energy losses and less electricity required as a result.
- The efficiency of your unit – higher efficiency units require less electricity to provide the same amount of heating or cooling.
Did you know that you can use a mini-split to heat your garage? Why not read our article on how to do this, here?
How Is Mini-Split Power Measured?
Mini-splits come in various sizes, usually defined in British Thermal Units per hour (Btu/h). A Btu is a measurement of heat energy and is equivalent to the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit.
When you buy electricity from your electricity company, it calculates your bill based on the kilowatt-hours you consume. A kilowatt-hour (kWh) is the energy used by a one-kilowatt device operating for one hour.
Therefore, you need to know how many kilowatts your system will consume and the price per kilowatt-hour your electricity company charges to calculate the cost of running your system.
There are several ways companies can calculate electricity consumption.
Mini-Split Data Sheet
If you have access to the technical specification data sheet for your mini-split, you might be able to find the power consumption there.
Simply multiply the power consumption in kW by the hours you will operate the unit daily, giving the number of kilowatt-hours of electricity consumed daily.
Next, multiply the kilowatt-hours by the price per kilowatt-hour your electricity company charges, and you have an estimated cost of running the unit.
According to the US Energy Information Administration, the average price of electricity in the US is $0.145/kWh. Assuming a heat pump consumes 1.2 kW and operates 12 hours a day, we can calculate the daily cost as follows:
1.2 kW • 12 hours • $0.145 = $2.09 per day
If the power consumption isn’t provided on the sheet, you can use the amps and volts instead. Most mini-splits are either 110V or 220V and need between 15 and 54 amps.
Once you’ve got the volts and amps from the specification sheet, multiply the two together to get the power in watts. Then you can multiply that figure by the number of hours per day you’ll run the unit and divide by 1,000 to get the number of kilowatt-hours.
For example, the power consumption of a 220V-unit, drawing 10 amps will be calculated as:
10 A • 220 V = 2,200 W = 2.2 kW
You can then calculate the kilowatt-hours and cost per day in the same way as illustrated above. However, information about power consumption isn’t always easy to find.
So, what should we do then?
How To Convert Btu/h to kWh Using Energy Efficiency Ratio (EER)
It’s possible to get a rough idea of how much electricity your mini-split will use by multiplying its Btu rating by its estimated hours of operation and converting it to kWh.
This calculation is easy to do—the conversion factor for Btu to kWh is 2.93 x 10-4, so the following example would give you the number of kWh of heat energy generated by a 12,000 Btu/h mini-split operating for 12 hours per day.
12,000 Btu/h • 12 hours • 2.93 • 10-4= 42.2 kWh
This calculation gives us the amount of heat energy the unit outputs in kWh, not the electrical energy consumption.
Mini-splits are very efficient, and because they move heat rather than generate heat directly, they require less electrical energy to run than the amount of heat energy they output. This efficiency is measured by the Energy Efficiency Ratio (EER) ratio.
The government-backed Energy Star symbol is awarded to products with high energy efficiency. The rating is intended to provide an unbiased and credible view consumers can use to make well-informed choices about which products to purchase.
To qualify for an Energy Star certification, air source mini-split heat pumps must have an EER of at least 12.5 Btu/Wh. Dividing the heating or cooling capacity of the unit by the EER will give the power consumption in watts.
So, for our 12,000 Btu/h example, we would calculate the electrical energy as:
12,000 Btu / h12.5 Btu/Wh = 906 W
If the unit runs for 12 hours a day, we will calculate the number of kilowatt-hours as:
906 W • 12 h = 10,872 Wh = 10.87 kWh
At a price of electricity of $0.145/kWh (the average in the US according to the US Energy Information Administration), we will calculate the cost per day as:
10.87 kWh • $0.145 = $1.58 per day
Multiply this by 30 days, and you get a monthly cost of $47.40 to run the mini-split.
Other Efficiency Factors Used for Mini-Splits
You’ll come across other factors that describe the efficiency of heat pumps. We’ll look at two of these, which attempt to describe the efficiency of a mini-split averaged across the whole heating or cooling season.
Heating Season Performance Factor (HSPF)
The efficiency of a heat pump is described by the Heating Season Performance Factor (HSPF), which measures the unit’s efficiency.
HSPF is a measure of the total heat provided by the heat pump over the entire heating season (in Btu) divided by the total electrical energy used by the heat pump (in watt-hours).
An HSPF factor of 8.5 is considered very efficient and is the requirement for a unit qualifying for an Energy Star qualification.
Seasonal Energy Efficiency Ratio (SEER)
There is a similar rating for air conditioners and mini-splits operating in the cooling mode called the Seasonal Energy Efficiency Ratio (SEER).
SEER is the total heat removed from the living space throughout an entire cooling season (expressed in Btu) divided by the total electricity consumed by the unit during that same season (measured in watt-hours).
A SEER rating of 15 or higher is required for an Energy Star certification.
Summary
Mini-split heat pumps are highly efficient and output more heat energy (or equivalent cooling) than the electrical energy they consume.
Just how much electricity they use depends on factors like home size, how big the difference is between the outside temperature and the desired indoor temperature, and the level of insulation in your home.
Your installer will be able to advise you on the likely electricity consumption for your specific situation. Still, you can get a ballpark estimate by using the power consumption information on the specification sheet for your heat pump or from the heating or cooling capacity in combination with the published energy efficiency ratio.
