Understanding EER2 Rating: New 2023 Efficiency Rating For AC Units

EER rating is the most basic energy efficiency rating for air conditioners. In 2023, the Department of Energy will introduce a new EER2 rating that will replace the existing EER rating. Let’s look at what the EER2 rating is and what changes we can expect for the minimum EER rating in 2023 (now EER2 rating).

At first, it seems that the EER rating and EER2 rating are the same:

• EER rating stands for Energy Efficiency Ratio. This AC energy efficiency rating will be used up until the 31st of December 2022.
• EER2 rating stands for Energy Efficiency Ratio 2. This is the new AC energy efficiency rating that will be used from the 1st of January onward.

The ushering in of the new EER2 rating has first been mentioned in the DOE 2016 10 CFR Parts 429 and 430 paper pertaining to the “Energy Conservation Program: Test Procedures for Central Air Conditioners and Heat Pumps”:

“The new appendix M1 establishes new efficiency metrics SEER2, EER2, and HSPF2 that are based on the current efficiency metrics for cooling and heating performance, but generally have different numerical values than the current metrics.” (DOE introducing EER2 rating, among other HVAC performance standards).

As we can see, a 10 EER rated AC will not be a 10 EER2 rated AC, as an example. In fact, the new EER2 rating is 4.1% lower than now older EER rating. Example: 10 EER rated AC unit will now be 9.6 EER2 rated AC unit.

While the calculation of the EER2 rating stays the same as for the EER rating, the difference between EER and EER2 rating is caused by different test conditions DOE tests air conditioners at. You can read more about the EER itself and what is a good EER for an air conditioner here.

Namely, the test conditions EER2 rating is measured under harsher test conditions than the test conditions we used to measure EER rating up till now. The main difference between EER2 and EER is caused by using different external static pressure (0.1 in. WC for EER and 0.5 in. WC for EER2).

We are going to look at:

• How the EER2 rating is calculated? The same calculation is used for EER rating.
• Difference in test conditions for EER vs EER2 causes a change in the numerical value of the EER2 rating as compared to the EER rating.
• EER to EER2 and EER2 to EER conversion charts. In 2023, we will start seeing EER2 on AC specification sheets and it is useful that we figure out what this EER2 rating means in terms of the more familiar EER rating.
• What is a good EER2 rating for air conditioners? We are primarily talking about portable and window AC units.

How EER2 Rating Is Calculated

Energy Efficiency Ratio (EER) is the simplest way how to determine the energy efficiency of air conditioners (albeit it’s not all that realistic, hence the introduction of the SEER and new SEER2 rating).

There is no change as far as how the EER2 is calculated as compared to the EER rating. Namely, in our article about understanding EER rating, we have pointed out that EER rating is calculated using this formula:

In short, we divide the air conditioning cooling capacity (expressed in BTU or British Thermal Units) by the maximum electric input (wattage).

Example: Let’s say we have a 10,000 BTU window air conditioner. In order to produce these 10,000 BTU of cooling output, it required a 1000-watt power input. Here is how the EER rating is calculated:

EER Rating = 10,000 BTU / 1,000 W = 10 EER

We use the same formula for calculating the EER2 rating. However, there is a big difference. Due to harsher test conditions for the EER2 rating measurement (we will cover this difference later on), the 10,000 BTU air conditioner will require more than 1,000 watts to produce the same cooling output.

Example: Due to harsher test conditions for the EER2 rating, the same 10,000 BTU window AC unit will require closer to 1,041 watt power input (4.1% more than 1,000 watts) to produce the same 10,000 BTU of cooling output. Here is how the EER2 rating is calculated:

EER2 Rating = 10,000 BTU / 1,041 W = 9.6 EER2

As you can see, what was in 2022 a 10,000 BTU 10 EER rated window or portable air conditioner, will in 2023 be a 10,000 BTU 9.6 EER2 rated air conditioner.

Here is what makes the difference:

EER2 Test Conditions Vs EER Test Conditions

The goal of all these energy efficiency metrics is to capture, as closely as possible, the real-time energy efficiency of air conditioners. While the EER rating was fairly good, the EER2 rating does, according to the DOE, more closely match the real-time energy efficiency (and thereby energy expenditure) of the AC unit.

The main difference between EER and the new EER2 rating are conditions under which these energy efficiency ratings are measured.

Both EER and EER ratings are measured at these test conditions:

• Outdoor temperature: 95°F
• Indoor temperature: 80°F
• Relative humidity: 50%

The test condition that the DOE is changing (prompting EER2 to replace EER) is the external static pressure. That is the pressure of air exiting the air conditioner unit. Here is the difference:

• EER rating uses 0.1 inches of water column (in. WC) external pressure test condition.
• EER2 rating uses 0.5 inches of water column (in. WC) external pressure test condition.

In short, the external static pressure (ESP) is 5 times higher when measuring the EER2 rating compared to the EER rating.

It seems that the DOE believed this higher pressure will better align with the real-life conditions of using split-system, window, and portable air conditions.

When this increase in pressure change is used in AC testing, there is about a 4.1% difference in the resulting energy efficiency ratio. In our example, the 10,000 BTU air conditioner has to use an additional 41 watts because the blower fan has to work against a bigger pressure.

How To Convert EER To EER2 And EER2 To EER?

We know that the current minimum EER rating is 12.2 EER. In the ‘Table II-4 Amended Energy Conservation Standards for Central Air Conditioners and Heat Pumps as Determined by the November 2016 Test Procedure Final Rule’ of the DOE’s document when they first mention the EER2 rating, they list the minimum EER2 rating to be 11.7 EER2.

This gives an idea of how to convert EER to EER2.

Namely, 12.2 EER is equal to 11.7 EER2. This is about a 4.1% difference; essentially, the EER2 rating is 4.1% lower than the EER rating because of the higher external static pressure the blower fan has to work against and accordingly expend extra watts.

Knowing this, we can now convert EER to EER2 and EER2 to EER. Let’s start with the EER to the EER2 conversion chart. You will need this one if you want to figure out what EER2 rating an older air conditioner with a certain EER rating has:

EER To EER2 Rating Chart

Here are some examples of how to convert EER to EER2:

• 8 EER is equal to 7.7 EER2.
• 10 EER is equal to 9.6 EER2.
• 12 EER is equal to 11.5 EER2.
• 14 EER is equal to 13.4 EER2.

You can also figure out what the EER rating is if you see the EER2 rating of the AC specs sheet using this table:

EER2 To EER Rating Chart

Here are some examples of how to think about air conditioner energy efficiency in 2023 and onward:

• 8 EER2 is equal to 8.3 EER.
• 10 EER2 is equal to 10.4 EER.
• 12 EER2 is equal to 12.5 EER.
• 14 EER2 is equal to 14.6 EER.

The key question many people have with this new rating is this:

What Is A Good EER2 Rating For An Air Conditioner?

When buying a portable air conditioner in 2023, for example, you will likely see the EER2 rating specified on the specs sheet. It might be 7 EER2, 9 EER2, 10 EER2, and so on. How to know if the EER2 rating is actually good; if it actually means you are looking at highly efficient air conditioner.

Portable Air Conditioners

In our post about the EER rating, we made an analysis that showed that the average EER rating for a portable AC unit is about 8.5 EER.

We don’t have 100s on new portable AC units with EER2 ratings to make the same analysis. However, we can deduct what is an average EER2 rating for portable AC units by converting what we know: 8.5 EER is equal to 8.2 EER2.

In short, any portable AC unit with an 8.2 EER2 rating or higher, has above-average energy efficiency. Good energy efficiency for a portable air conditioner would be 9 EER2, 10 EER2, and so on. The higher the EER2 rating, the better (prices of portable AC units will likely increase with the higher EER2 rating as well).

The most energy-efficient portable AC units can surpass the 10 EER rating. That is equal to a 9.6 EER2 rating. You can check these energy-efficient portable AC units here; dual-hose units like Whynter portable ACs can have an 11 EER rating or 10.5 EER2 rating.

Window Air Conditioners

We can do a similar average EER to EER2 conversion for window air conditioners. Window AC units have an average EER rating of about 10 EER. That is equal to a 9.6 EER2 rating.

The most energy-efficient window AC units can have a 12 EER rating or even higher. That is equal to 11.5 EER2 or higher. You can check these energy-efficient window AC units here.

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All in all, the introduction of Energy Efficient Ratio 2 (EER2) should give us a more realistic idea of how energy-efficient air conditioners are. We have explained what EER2 rating is based on different external static pressure; this is the rating we are going to use from 2023 onward.

Obviously, there will be some adaptation pains at first. That’s why you can always consult the EER to EER2 and EER2 to EER charts above to help with this transition.