What size MRCOOL mini split AC do you need? (BTU calculation)
Tracy Beard / Tuesday April 2, 2024
MRCOOL is a popular brand of ductless mini-split air conditioners and heat pumps. These units offer an efficient way to heat and cool specific rooms in a home without the need for a complete HVAC system.
Let’s unpack everything you need to know about selecting the right MRCOOL unit size for your personal space.
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Why the size of your MRCOOL AC unit matters
If you’re considering purchasing a MRCOOL unit, one of the most important factors is the size of your space. An improperly sized unit will struggle to maintain a comfortable temperature and cost more money to operate over time. If the unit is too small, it won’t provide enough warmth or chill. If the unit is too large, it could short cycle, which can reduce the system’s lifespan, and decrease its efficiency.
What are BTUs and how do they impact your living space?
BTU stands for British Thermal Unit, which is a unit of measurement for heat energy. In heating and cooling systems, BTUs are used to measure the amount of heat an appliance can add or remove from a space per hour. Determining the right BTU rating for your living space depends on several factors including the square footage, insulation, ceiling height, number of windows and local climate.
In cooling systems such as air conditioners, BTUs indicate the cooling capacity of the appliance. A higher BTU rating means the air conditioner can remove more heat from the indoor air, so the machine will cool faster. An oversized air conditioner in a small space may cool too quickly, which can lead to humidity issues and inefficiency. An undersized unit may struggle to adequately cool a large area. Picking the right size system will help you maintain a consistent temperature, provide adequate airflow and minimize energy consumption.
The total square footage of an indoor space determines the baseline for heating and cooling. As a general guideline, MRCOOL ductless systems require about 20 BTUs per square foot. For example, a 500-square-foot room would need a 10,000 BTU unit.
How to calculate the right size MRCOOL unit for your space
You can follow some basic steps to estimate the correct capacity MRCOOL unit for your room or rooms:
1. Measure the space
Calculate the total square footage by multiplying length x width for each space. Remember to include all the rooms you wish to heat/cool.
2. Use a BTU calculator
Input the dimensions into an online BTU calculator for an estimate. You can find free BTU calculators on several different websites.
Then you can add the square footage, climate, windows, insulation and other details.
Common room sizes with recommended MRCOOL unit size
- 500 square foot living room – 10,000 BTU unit
- 750 square foot open concept kitchen and living area – 15,000 BTU unit
- 1,000 square foot basement recreation room – 20,000 BTU unit
- 2,000 square foot open concept main floor – 36,000 BTU unit
IMPORTANT: If there’s not a unit exactly sized for your space, use the next size up. It’s also recommended to contact a licensed HVAC technician to confirm the appropriate heating/cooling load for your space.
3. Get a professional consultation
While online BTU calculators can give a general guideline for unit capacity, MRCOOL recommends that users of its products have a licensed HVAC technician assess their heating and cooling requirements before installation for the following reasons:
- Technician’s previous experience
- The technician’s ability to account for all influencing factors
- Access to advanced load calculation software
- Proper installation
- Technician’s ability to combine rooms in the best configurations
- Establish ongoing maintenance and service for your specific system
How to find a reputable HVAC technician
- Ask friends and neighbors for referrals
- Check online reviews from past clients
- Check for the proper licensing from your state
- Ask about experience installing ductless systems
- See if they offer ongoing maintenance contracts
- Check for detailed quotes that outline all provided services
Other factors to consider before purchasing a MRCOOL ductless AC
Climate and temperature range
- Outdoor temperatures affect the unit’s delivery
- Hotter climates require larger capacity units to handle higher heat loads
- Colder climates need a larger capacity for very low outdoor temperatures
Insulation
Well-insulated spaces are easier to heat and cool. If you have poor insulation, heat and cool air will transfer more easily, so you may need a larger unit.
Windows and doors
- More and larger windows and doors allow for more heat transfer
- North-facing windows get more sun exposure in the Northern hemisphere
- Window treatments (blinds, curtains, etc) help regulate heat gain/loss
More factors
- Ceiling height (higher ceiling = more space to heat or cool)
- Occupancy (more people means more body heat to cool)
- Rooms with many appliances and electronics that produce heat may increase the required load
MRCOOL unit size options
MRCOOL offers a range of ductless mini-split unit sizes to handle different room requirements:
- 12,000 BTU
- 18,000 BTU
- 24,000 BTU
- 30,000 BTU
- 36,000 BTU
The unit capacity describes the cooling power using BTUs or British Thermal Units. ]
The general guideline is 20 BTUs of unit capacity per square foot for residential spaces. But the actual heating and cooling load depends on all the factors described in the previous section.
More information & where to buy
Thanks for stopping by! We hope this guide helped you determine what size MRCOOL unit you need for your space.
If you run into any issues, just give us a call at 1-877-477-7278 or start a chat with a pro on our website so we can help you through it. We’ve got many more troubleshooting and repair guides on our DIY blog and YouTube channel and all the parts you need to do it yourself at AppliancePartsPros.com.
Hello there! I’m Tracy, and I’m thrilled to be part of the Appliance Parts Pros team. With two years of service and hands-on experience here, I’ve had the privilege of helping numerous customers troubleshoot their home appliances and find DIY repair solutions.