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 95F to 80F temperature difference.

**SEER** = ‘**S**easonal **E**nergy **E**fficiency **R**atio’ measures energy efficiency throughout the summer season (June, July, August). We can consider it as a real-time every EER.

Here is the most universal **EER to SEER converter**. Just input the EER rating and you’ll get the SEER rating (yes, the calculator is free to use):

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:

$SEER=\frac{1\times {\mathrm{EER}}_{100\%}+42\times {\mathrm{EER}}_{75\%}+45\times {\mathrm{EER}}_{50\%}+12\times {\mathrm{EER}}_{25\%}}{100}\phantom{\rule{0ex}{0ex}}$On air conditioner’s specification sheets we usually get EER rating (many times without SEER rating). However, the EER specified on the specs is EER_{100%}. That makes it impossible to convert from EER to SEER exactly.

We can, nonetheless, get a close estimate of what SEER rating is from the EER ratio.

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:

$EER\hspace{0.17em}=0.875\times SEER$

Using this less-accurate but more general formula, we have created the most 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.

## EER Below 14 (EER To SEER Calculator)

For EER up to 14, you can use a more accurate EER to SEER calculator here. Just input EER rating and you’ll get SEER rating:

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

$SEER=\frac{1.12\u2013\sqrt{1.2544\u20130.08\times EER}}{0.04}$

Here are a few examples:

- Air conditioner with an 8 EER has a 10.68 SEER rating.
- AC unit with 10 EER rating has a 13.86 SEER rating.
- The LG LP1419IVSM portable air conditioner with 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%}.

In order 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%}, 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.