What Is Seer?

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If you’ve ever had to choose a new air conditioner, it’s likely that you’ve heard the term ‘SEER’ thrown around once or twice. It’s also likely that you had no idea what the term meant. So what exactly is SEER?

SEER stands for Seasonal Energy Efficiency Ratio and it is a mathematical ratio that can determine the efficiency of a particular HVAC system. Similar to how miles per gallon is used to judge your car’s efficiency, SEER is used to determine your AC’s efficiency. In general, the higher the SEER, the less electricity the system needs to perform its job, making it more energy efficient and better for your wallet.


Prior to SEER, there was no universal standard of measurement to determine and air conditioner’s energy efficiency. In order to rate the cooling efficiency of AC units, the Air Conditioning & Refrigeration Institute introduced the EER (Energy Efficiency Ratio) in 1975.

The purpose of the EER was to rate the cooling output of an air conditioning unit in BTU’s (British Thermal Units) each hour, divided by the input of energy in watts of electricity. These had to be at a specific humidity and temperature for it to measure the input and output conditions.


A cooling device’s EER is the ratio of output cooling energy in BTU’s to input electrical energy in watts in a single operating condition. EER differs from SEER which denotes a cooling device’s expected overall performance for one year in a certain location.

Unlike SEER, EER is measured at one set of conditions and typically provides more realistic measurements of energy efficiency. SEER on the other hand, is a seasonal average over a specified range of conditions. EER ratings came before the SEER ratings, but both are still used today to measure energy efficiency, although EER tend to be used on large commercial units.

SEER Requirement Changes in 2015

Since 2011, the US Department of Energy has been revising rules to raise the standards for residential HVAC systems. Starting January 1st, 2015, split system air conditioners in the southeastern region of the US are required to be rated at least at 14 SEER. As for the southwest region, HVAC units will be required to be 14 SEER and 12.2 EER while all other remaining states will have a minimum 13 SEER requirement.

To learn more about about energy efficiency, contact One Hour Heating & Air Conditioning® of Largo.