EER and SEER both measure the energy efficiency of HVAC devices such as air conditioners and heat pumps.

**EER** = ‘**E**nergy **E**fficiency **R**atio’ measures energy efficiency at 100% cooling load, 50% humidity, and 95°F to 80°F temperature difference.

**SEER** = ‘**S**easonal **E**nergy **E**fficiency **R**atio’ measures energy efficiency throughout the summer (June, July, August).

You can read what is the difference between EER and SEER here.

Here is a universal **EER to SEER converter**. Just input the EER rating, and you’ll get the SEER rating. If you need to convert SEER to EER, you can check the SEER to EER converter here.

Inversely, if you have SEER and would like to calculate EER, you can use this SEER to EER calculator.

Here is the **EER to SEER chart** for some key EER ratings:

The formula of how to convert EER to SEER is:

SEER = (1 × EER_{100%} + 42 × EER_{75%} + 45 × EER_{50%} + 12 × EER_{25%})/100

In air conditioner specification sheets, we usually get an EER rating (many times without a SEER rating). However, the EER specified on the specs is EER_{100%}. That makes it impossible to convert from EER to SEER exactly.

Nonetheless, we can get a close estimate of what the SEER rating is from the EER ratio. For example, mini-split systems only use the SEER rating instead of the EER rating.

At EER ratings above 14, the missing measurements of EER_{25%}, EER_{50%}, EER_{75%} have a much bigger impact. Therefore any EER to SEER calculation contains a potentially larger measurement error.

Nonetheless, HVAC experts from AHRI (Air-Conditioning, Heating, and Refrigeration Institute) recommend using a simple and universal formula to calculate SEER from given EER. Here’s the formula:

**EER = 0.875 × SEER**

Using this less-accurate but more general formula, we have created a universal EER to SEER calculator (you can see it at the beginning of this article). There you can also see SEER ratings for different EER ratings in a chart.

This EER to SEER conversion is most appropriate for below 14 EER values. Most AC units fall in these categories. For example, you can check out some of the most energy-efficient AC units and see that all of them have an EER rating below 13:

- Portable AC units with 11+ EER rating here.
- Window AC units with up to 12 EER rating here.
- Ductless mini-split AC units with about 10-12 EER rating here.

## EER Below 14 (EER To SEER Calculator)

For EER up to 14, you can use a more accurate EER to SEER equation.

The EER to SEER calculation is based on a close approximation illustrated by the following formula:

**SEER = (1.12-√(1.2544-0.08*EER)) / 0.04**

Here are a few examples:

- Air conditioner with an 8 EER has a 10.68 SEER rating.
- AC unit with a 10 EER rating has a 13.86 SEER rating.
- The LG LP1419IVSM portable air conditioner with a high EER rating (EER = 10.14) has a 14.04 SEER rating.

It pays to keep in mind that these calculations of SEER are based only on EER_{100%}.

To truly calculate the SEER rating, a manufacturer has to measure EER rating at 4 different partial cooling loads, namely EER_{25%}, EER_{50%}, EER_{75%}, and EER_{100%}. Only in such a way we can calculate true SEER from EER because SEER is, in essence, a weighted average of these partial loads.

Other similar cooling energy efficiency ratings include the IEER rating and the ESEER rating, for example.

Thank you for this excellent article. I wonder if you know why an AC unit is Energy Star Compliant in the US, but the same AC is not Energy Star Compliant in Canada? The Insignia NS-AC8WU3 (sold in US only) is 15 SEER and ES Compliant (has the ES logo on front), however the Insignia NS-AC8WU3-C (only sold in Canada) is not ES Compliant, and it only has an EER (not SEER) of 10.9. Insignia offers no help, says it is the same machine but won’t say if the model Canada is less energy efficient. Do you have any insights on why the same model (supposedly) would not qualify as Energy Star in Canada?

Hello Frieda, I can see the problem, yes. In general, this can be explained in two ways; either Energy Star requirements in the US vs Canada differ or the producer didn’t choose to pursue Energy Star certification in Canada. We are looking at the U-shaped 8,000 BTU window AC by Insignia, right? These are the same AC units with a CEER rating of 15.0. That’s a very good rating; you can read more about CEER rating for room air conditioners here.

In this case, it seems that Insignia has not yet applied or their application is processing for Energy Star rating. Regardless of this, this Insignia window AC unit seems to have a very good EER rating. Hope this helps.