What is SEER and SEER2?

SEER is the rating system for air conditioner and heat pump energy efficiency. It stands for Seasonal Energy Efficiency Ratio. The higher the number, the less electricity the air conditioner or heat pump consumes.

SEER2 is the upgraded version of SEER. SEER2 became the new standard energy efficiency rating system for air conditioners and heat pumps on January 1, 2023. All new air conditioner models manufactured from 2023 on will carry a SEER2 rating.

How are SEER and SEER2 Ratings Calculated?

SEER is the calculated in the following way:

The total amount of heat removed from a home during a typical annual cooling season (expressed in British thermal units (BTU1))

divided by

The total electrical energy the air conditioner or heat pump system used during the same cooling season (expressed in watt-hours (Wh))2.

SEER2 uses this same calculation as SEER. The difference between SEER and SEER2 ratings lies in the testing procedures.

Each air conditioner must undergo testing to determine its efficiency rating. On January 1, 2023, new testing requirements came into effect, which include some adjustments to account for actual field conditions. For instance, manufacturers are now required to test air conditioners and heat pumps under higher external static pressure.

The result is a more accurate representation of a unit’s energy consumption in the real world. However, the SEER rating a unit achieves under the new testing procedures is approximately 4.5% lower than the rating it would have received under the old testing requirements. To differentiate units tested under the old and new requirements, the new efficiency rating is referred to as SEER2.

Comparing SEER and SEER2 is a bit like comparing apples and oranges. However, a SEER2-rated system is roughly 4.71% more efficient than a SEER system with the same rating number. To test this out on the SEER Savings Calculator, try setting the SEER and SEER2 sliders so the number on both sliders is the same. (The resulting energy cost savings estimates will round up to the next whole percentage point.)

For a more in-depth explanation of SEER2 calculations and testing requirements, feel free to hunker down for some further reading in the following document: AHRI Standard 210/240 (210/240-2023)

1A British thermal unit (Btu) is essentially a unit of heat. 1 Btu is equivalent to the amount of heat it takes to raise the temperature of one pound of water by one degree Fahrenheit.

2 US DEPARTMENT OF ENERGY (DOE), 10 CFR Parts 429 and 430, [Docket No. EERE-2016-BT-TP-0029] RIN 1904-AD71, Energy Conservation Program: Test Procedures for Central Air Conditioners and Heat Pumps, page 194

A Note About HSPF and EER

We should also note two other HVAC energy efficiency acronyms you might come across – HSPF and EER. While these are not mentioned on our AC energy savings calculator, it’s important to know what they mean.

HSPF (Heating Seasonal Performance Factor) and HSPF2

Heat pumps have an HSPF rating in addition to a SEER rating. HSPF (Heating Seasonal Performance Factor) rates a heat pump’s heating efficiency. The only difference between a heat pump and an air conditioner is that a heat pump can provide both heating and cooling. A heat pump cools your home by transferring warm air from the inside to the outside, and it heats your home by transferring warm air from the outside to the inside.

Like SEER, HSPF is calculated by dividing the total BTU1 required to heat your home during a typical season by the total watt-hours of electricity the heat pump consumes during that same season.

Also like SEER, HSPF underwent changes to the rating system in 2023. We won’t go into details here, but suffice to say that all heat pumps manufactured in 2023 and beyond will have an HSPF2 rating, replacing the former HSPF rating.

Use our AFUE Savings Calculator to learn more about HSPF and heat pump energy efficiency.

EER (Energy Efficiency Ratio) and EER2

EER, standing for Energy Efficiency Ratio, is also a measurement of air conditioner or heat pump energy efficiency. Starting January 1, 2023, EER2 is the updated version of EER.

EER2 is calculated in a nearly identical manner to SEER2 (BTU/Wh). However, the main difference between the two is that SEER2 accounts for changes in the average outdoor temperature and EER2 does not. EER2 is based on a constant outdoor temperature of 95° F. On the other hand, SEER2 calculations are based on outdoor temperatures ranging from 65°F to 104°F.

Because SEER2 factors in seasonal performance, it is considered the standard rating system. EER2’s specific temperature scenario has limited real-world application, making it less useful as a measure of actual efficiency.