What Is a SEER Rating?

by Pete Lader June 29, 2022

Source: DifferR / Shutterstock.com

If you’ve ever browsed mini split air conditioners, you probably know that each product has a long list of numbers and specifications. One of these specifications is the SEER rating, found on virtually all HVAC products. A mini split’s SEER rating is one of its most critical specifications. Learn about the rating’s definition, how SEER is calculated and what constitutes a good SEER rating.

Definition of the SEER Rating

SEER stands for Seasonal Energy Efficiency Ratio. The SEER rating was defined and standardized in 2008 by the Air Conditioning, Heating, and Refrigeration Institute (AHRI) in the AHRI 210/240 standards document. The current version of the SEER rating standard is SEER2, as defined in AHRI 210/240-2023.

An air conditioner’s SEER rating is a number value determining its cost-efficiency over an average cooling season. The higher the SEER rating, the less energy it needs to output its cooling capabilities. For example, when comparing two 3-zone mini split systems with the same cooling power, the model with the higher SEER rating consumes less energy to operate than the model with the lower SEER rating.

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a mini split ac condenser mounted on a wall

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How a SEER Rating Is Calculated

To understand the SEER rating, you must first understand another rating system: the Energy Efficiency Ratio or EER.

The EER Rating

EER is a simple calculation: It corresponds to the air conditioning unit’s theoretical maximum cooling output (measured in British Thermal Units per hour) divided by the power input (the maximum number of watts).

  • Example: A dual-zone mini split system rated at 18,000 BTU consumes up to 1,200 W of electricity. 18,000 divided by 1,200 equals 15; therefore, the EER of this unit is 15.

However, EER only calculates the relative efficiency at maximum output. Mini split air conditioning systems are not designed to run at 100% output all the time. Under normal usage conditions, a mini split’s load frequently varies, often fluctuating between 25% and 75%.

Calculating the SEER Rating

The SEER rating calculation is intended to represent the efficiency of an air conditioner during a typical cooling season (1,000 hours, or eight hours per day for 125 days per year). This calculation method relies on real-world performance measurements instead of a simple formula, making it a more accurate representation of the system’s efficiency than EER.

During a typical cooling season, the AC unit runs at various output percentages instead of a fixed 100% output. The SEER rating is calculated by adding the total amount of heat removed (in BTUs) during a 1,000-hour season divided by the total amount of watts used during this season. 

  • Example: Your 18,000 BTU dual-zone system has removed 14,200,000 BTU and consumed 887,500 W of electricity over 1,000 hours of operation. 14,200,000 divided by 887,50 equals 16. Consequently, the SEER rating of this system is 16.

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What SEER Ratings Do I Need?

According to the Department of Energy, as of June 2022, all room air conditioners and heat pumps sold in the United States must feature a minimum SEER rating of 10. However, the Energy Information Administration has indicated that starting on January 1, 2023, a new set of minimum efficiency standards will go into effect. According to the 2023 regulation standards, split system air conditioners with an output of less than 45,000 BTU must be tested according to the SEER2 standards and feature a minimum SEER2 rating of 13.4. If you live in a southeastern or southwestern state, the minimum SEER2 rating is 14.3.

The general rule with SEER ratings is simple: The higher the number, the less it costs to operate, and the higher the cost-efficiency. High-quality air conditioning units, such as the MRCOOL mini split family of products, easily surpass the federal minimum values, saving you considerable money on your energy bills. For example, the MRCOOL 30,000 BTU 3-zone mini split unit is rated at SEER 21.5, making it a highly efficient system. Compared to a unit of the same power with a SEER rating of 15, the MRCOOL system costs approximately 30.5% less to operate. 

a man using a remote to control a mini split unit

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Save Money on Your Energy Bills with Premium Home Source

Premium Home Source is a family-owned company founded in 2007 that understands the importance of sourcing high-quality, high-efficiency home appliances, from ovens to air conditioners. We made it our mission to help homeowners find the best quality equipment to outfit their homes at the best possible prices. Whether you want to learn more about mini splits or are looking for highly efficient mini split air conditioners or other equipment for your kitchen, bathroom, living room or even outdoor furniture, we offer everything you need with the quality you deserve. For more information, contact us at (800) 805-7102.


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