EER To SEER2: How To Make Conversion? (+ Conversion Chart)

AC energy efficiency matters a lot. We use a lot of different energy ratios to express energy efficiency. With older portable and window AC units, you will see they have an EER rating (Energy Efficiency Ratio). With the newest (2023 and beyond) air conditioners, you might see a SEER2 rating (Seasonal Energy Efficiency Ratio 2).

How do EER and SEER2 compare? We will show you how you can roughly convert EER to SEER2 and point out the differences between the two efficiency ratios. We also created an EER to SEER2 conversion chart with 6-20 EER converted to SEER2.

Example: Let’s say you have a 12 EER window AC unit and would like to know how much SEER2 is 12 EER. You can calculate that manually (we will show you how to do it) or just consult the chart below; you will see that 12 EER is roughly equal to 13.1 SEER2.

EER Vs SEER2

Let’s first look at both of these energy ratios:

• EER is the old pre-2023 ratio that measures energy efficiency measured at 100% cooling load, 50% humidity, 80°F indoor temperature, and 95°F outdoor temperature. It has been replaced with the new EER2 rating.
• SEER2 is the new post-2023 ratio that measures seasonal energy efficiency (throughout the year). It doesn’t presume that an AC runs at 100% cooling load all the time. Rather, it presumes a more realistic AC cooling; SEER2 assumes the AC is running at 100% output only 1% of the time, at 75% output 42% of the time, at 50% output 45% of the time, and at 25% output 12% of the time.

In fact, the old SEER rating is calculated based on old partial EER ratings, and the new SEER2 rating is based on the new partial EER2 ratings. Here are the equations for both SEER and SEER2:

Pre-2023: SEER = (1 × EER_100% + 42 × EER_75% + 45 × EER_50% + 12 × EER_25%)/100

Post-2023: SEER2 = (1 × EER2_100% + 42 × EER2_75% + 45 × EER2_50% + 12 × EER2_25%)/100

Now, the rough conversion from EER to SEER is described with the formula:

EER = 0.875 × SEER

Basically, EER is about 15% lower than the SEER rating. However, in 2023, new HVAC energy efficiency ratios were introduced, including EER2, SEER2, and HSPF2.

In our SEER vs SEER2 article here, we calculated that SEER2 is about 4.5% lower than the old SEER (Example: 14 SEER is now 13.4 SEER2). Based on this, we can roughly convert EER to SEER2:

How To Convert EER To SEER2? (Formula)

For EER to SEER conversion, we need to combine these 2 equations:

EER = 0.875 × SEER

SEER2 = 0.955 SEER

By expressing SEER from the 2nd equation and inputting the result in the 1st equation, we get the following EER to SEER2 formula:

SEER2 = 0.955 × EER / 0.875 = 1.09143 × EER

We need to multiply the EER rating by a factor of 1.09143 to get SEER2. That means that SEER2 should be a good 9% higher than EER.

Quick Example: What is the SEER2 rating of an 11 EER AC unit? We simply input 11 EER in the equation above like this (with the result):

SEER2 (11 EER) =  1.09143 × 11 EER = 12.00 SEER2

We see that 11 EER is equal to about 12 SEER2.

This is just 1 example. To help everybody out – calculating this by hand is a bit tedious – we converted 6-20 EER ratings to SEER2 ratings and consolidated all the results in the all-encompassing conversion chart:

EER To SEER2 Conversion Chart

Now, whenever you need to convert EER to SEER2, you can just check this chart. Here are a few examples:

• 8 EER is equal to about 8.7 SEER2.
• 10 EER is equal to about 10.9 SEER2.
• 12 EER is equal to about 13.1 SEER2.
• 14 EER is equal to about 15.3 SEER2.

We hope this helps you with the conversion. If you have any questions or would like us to calculate something for you, you can give us the numbers in the comment section below, and we will help you out. Thank you.