What Are SEER & EER Ratings? A Guide to AC Energy Efficiency Ratings

If you skim through any AC listing, you’ll notice something called a SEER rating or EER rating. Sometimes, you’ll notice both. These numbers can play a big role in the AC shopping process.

But what are SEER ratings, exactly? What do they mean? What is an EER rating and how is it different? Both of these ratings are crucial to choosing an AC, but there are some key differences between them that are important to know before you purchase a new unit. 

In this article, we’ll explain what EER and SEER mean, and how to determine which air conditioning efficiency rating is right for your home.

About Air Conditioning Efficiency

An AC unit’s energy efficiency rating (EER) is determined by the unit’s cooling output (measured in BTUs) divided by how much energy the unit consumes (in watts) during one hour of cooling. The higher the number, the more energy efficient that unit is.

Higher efficiency units are typically more expensive to purchase compared to their lower efficiency counterparts, but the investment can be worth it in the long run. According to the Energy Information Administration, heating and cooling account for more than half of the energy consumed by US households.

An energy efficient unit can save you thousands each year in energy bills, and efficient units are better for the environment as well. This is why EER and SEER ratings are important when it comes to AC units.

What is EER?

EER (now EER2) stands for Energy Efficiency Ratio and is an objective measurement of how efficiently an AC unit is engineered to run. 

This is determined by several parameters during testing:

• A set outdoor temperature of 95° F
• A set indoor temperature of 80°
• A relative humidity level of 50%
• 0.5 in. WC static pressure

The higher the EER rating, the more efficient the AC is. Units with an EER rating of 11 or higher are considered efficient. The EER is always displayed in the Energy Label sticker required for all AC units in the US.

What is SEER?

SEER (now SEER2) stands for Seasonal Energy Efficiency Ratio and is a measurement of how efficiently a unit will operate over one cooling season. Unlike EER ratings, SEER ratings are determined by varying indoor/outdoor temperatures as well as varying humidity levels, and the rating takes into consideration temperatures ranging from 60-100° F. This makes them a more accurate measurement of the AC unit’s efficiency.

SEER ratings are also only used for mini-split HVACs and central air systems, which are larger and use more energy than smaller units such as window or through-the-wall ACs. Like the EER rating, the SEER is displayed in the EnergyGuide label attached to mini splits and central air.

Mini split SEER ratings are highly useful in helping homeowners predict their overall energy expenditures for the season, but choosing a unit based on SEER ratings requires a bit more knowledge than the number alone. SEER ratings do not take into consideration average regional temperatures over a cooling season. This means a unit that is energy efficient in Seattle is not necessarily going to be efficient in Santa Fe where average temperatures are much higher, especially in the summer.

EER vs SEER: What’s the Difference?

EER measures the AC unit’s efficiency at peak cooling operation, representing the hottest time of the year. SEER provides a more rounded measurement by measuring the efficiency across the whole cooling season, through a fluctuating range of temperatures and humidity levels.

In general, EER ratings are used for smaller room air conditioners like window and through-the-wall models. Larger cooling units like mini splits and central air systems use SEER, which provides a more accurate assessment of their efficiency.

In addition, unlike EER, there is a minimum SEER rating for residential air conditioners and heat pumps sold in the US. The minimum ratings vary by region.

What is SEER2?

In January 2023, the EPA introduced SEER2, which is an updated standard for SEER. SEER2 is derived from a new testing standard from the Department of Energy, which takes into account new external static pressure conditions that better reflect real-world conditions.  

To know more, check out our detailed guide to SEER2 for consumers and contractors.

Which air conditioner SEER rating do I need?

The DOE breaks the country down into three regions — North, South, and Southwest — with different energy requirements for each. Under SEER2, the federal minimum for all regions by 1 SEER. SEER2 applies to AC units including central air conditioners and ductless mini splits, as well as heat pumps.

Keep in mind that AC SEER ratings are only used for mini-split HVACs and central air systems. For window or through-the-wall units, you’ll want to pay attention to EER ratings. There are new legally mandated minimum ratings for window and through the wall units. Window ACs also use a different measurement of efficiency known as CEER.

Which air conditioner EER rating do I need?

If you are looking to purchase a window or through-the-wall AC, you will need to look for a unit with an EER rating of at least 10.8 (Northern region) or 12.2 (Southern and Southwest regions).

All mini-splits and whole-home solutions have EER ratings as well, so look for that number in addition to that unit’s SEER rating to ensure the AC you choose is appropriately efficient all-around.

Examples of energy efficient AC units

Now that you know the difference between SEER and EER ratings, you’re probably wondering which energy efficient air conditioner solution is right for you.

Total Home Supply carries a wide selection of energy efficient AC units with both high SEER and EER air conditioner energy ratings. Here are a few options:

Single-zone mini split with high SEER:

Friedrich FRHW093A 9000 BTU Floating Air Premier Series Single Zone Mini Split with Built-In WiFi – Heat and Cool – Energy Star

The Floating Air Premier Series is Friedrich’s top of the line ductless mini split systems, boasting Energy Star certification and high SEER ratings. This system has great efficiency ratings of 27.5 SEER2 and 16.1 EER. 

This model provides 9,000 BTUs of cooling and 10,500 BTUs of heating. It can service a room that is about 450 sq. ft. The built-in low ambient cooling capabilities will cool your space when outside temperatures are as low as 0°F. The heat pump can provide 6,500 BTUs at 17°F but with its low ambient heating capacity, will provide heat even with temperatures down to -13°F.

It also has inverter technology, where the compressor runs at a lower speed instead of shutting off completely. This helps the system to maintain the set temperature, alleviating the need for the system to start up again from a completely shut down state.

Multi-zone mini split with high SEER:

Friedrich FPHMR18A3A 18000 BTU Floating Air Pro Two Zone Mini Split Air Conditioner with Heat Pump

This dual-zone system can service two separate spaces. It delivers 18,000 BTUs of cooling, with a connected capacity of up to 24,000 BTUs. Allowable units include Friedrich’s standard wall unit, 4-way ceiling cassette as well as a ceiling concealed duct unit. These indoor units can be mixed to fit your installation requirements. Each unit works with its own remote (included with wall and ceiling cassettes) or wall controller (included with concealed duct units) allowing for individual comfort control.

Depending on your installations of non ducted, ducted, or mixed units, the FPHMR18A3A gets great energy ratings.

Connected Units	EER	SEER	HSPF
Non-Ducted Indoor Units Only	12.5	22.0	11.0
Ducted Indoor Units Only	11.5	19.0	9.6
Mixed Non-Ducted and Ducted Indoor Units	12.0	20.5	10.3

The outdoor unit features Low Ambient Operation making it a great year round option for heating and cooling for most of the US. It will operate in the Cooling Mode when outdoor temperatures are as low as 14°F up to 115°F. The range in which this unit will heat is equally as wide and it will heat when temperatures are as low as -13°F up to 75°F!

If you have any additional questions regarding SEER/EER ratings or energy efficient cooling units, please do not hesitate to contact us at 877-847-0050 and speak to one of our qualified AC specialists.

You can also check out our other articles on AC energy efficiency:

Energy Efficient AC Units: What to Look for in a High Efficiency AC

The Efficiency of Mini Split ACs and Why They’re a Great Investment

Mini Split vs Central Air/Heat: Which is Right for You?