Convert EER to SEER (Calculator + Conversion Table)

EER and SEER are efficiency measurements that vary slightly because of how they’re calculated. That’s the topic of this guide – How to Convert EER to SEER.

You might want to convert EER to SEER if you’re comparing two air conditioners and don’t have the values for both. That’s one of the aggravating things about AC product pages and other marketing material. They are often incomplete, including one measurement but not both.

EER to SEER Calculator

Here is our “Convert EER to SEER” Calculator which can help you get the result quickly.

EER to SEER Calculator

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

EER RatingSEER Rating
10 EER 11.15 SEER
11 EER 12.70 SEER
12 EER 14.44 SEER
13 EER 16.42 SEER
14 EER 16.00 SEER

Convert EER to SEER

You can do it the hard way or the easy way, and the numbers come out about the same.

Converting EER to SEER When EER is Below 14

This is a very technical approach, but a precise one, using this formula:

\(SEER = frac{1.12-sqrt{1.2544-0.08times EER}}{0.04}\)

If your math is a little rusty, then here is a step-by-step for working the EER to SEER calculator formula:

1). Multiply EER by 0.08, and write down the number you get.

2). Subtract that number from 1.2544

3). Find the square root of the number you get. The easiest way is to use the square foot function on your calculator. It has this symbol in it:

You might want to jot down that number out to 4-6 places, depending on how accurate you wish to be.

4). Subtract that number from 1.12

5). Divide that number by 0.04.

OK, let’s use the formula and steps to convert 10 EER to SEER:

1) 0.08 x 10 = 0.8

2) 1.2544 – 0.8 = 0.4544

3) The square root of 0.4544 = 0.67409198

4) 1.12 – 0.67409198 = 0.44590

5) 0.44590 / 0.04 = 11.1477

10 EER = 11.15 SEER (rounded off)

Converting EER to SEER When EER is Above 14

When EER is above 14, the initial step of multiplying 0.08 by EER will yield a number larger enough that the result of subtracting it from 1.2544 will produce a negative number (step 2 above). That makes it impossible to use this formula for converting EER to SEER.

So, there’s an easier way, though not quite as accurate. It is to divide EER by 0.875 to get SEER.

It’s written \(SEER = frac{EER}{0.875}\)

In fact, you can use this with any EER, whether 14, above or below, though the result is as accurate. For example, using the complex equation, we came up with 10 EER = 11.15 SEER.

Using the easier formula, 10 EER = 11.4 SEER. Close, but not as accurate.

EER vs SEER – Which is Better?

EER is a more accurate reflection of the air conditioner’s sheer ability to remove heat from the air. But the advantage of SEER is that it gives you a broader perspective. Here’s what we mean.

EER is the Energy Efficiency Ratio of an air conditioner. It is usually used to rate the efficiency of geothermal heat pumps in AC mode, but increasingly is being used for most other types of air conditioners.

EER is measured when the AC is running at 100% capacity (some air conditioners have multiple stages that are less than 100%). The measurement is done under controlled conditions – 95F outside temperature, 80F indoor temperature and 50% relative humidity.

How many BTU’s of heat can the unit remove under those conditions? That’s EER. The formula is EER = 1.12 x SEER – 0.02 x SEER squared.

SEER is Seasonal Energy Efficiency Ratio. It measures how efficiently the air conditioner operates under various conditions throughout the year. Using a standard indoor temperature, efficiency is measured in 8 varying outside temperatures from 65F to 104F

The SEER equation considers BTUs moved during the season by the watts/kilowatts needed to do the job.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.
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