SEER vs EER – Understand What SEER is, What EER is and When to Use Each.

We often get asked questions about SEER ratings, but those that have done

a little research know that EER is also a useful means of measuring an air

conditioner’s efficiency, which leads one to ask the question, when looking

at SEER vs EER, which do you choose? If you’ve read some of our articles,

you know that we are straight shooters and have no loyalty to any specific

company on means of measurement. In short, we are unbiased. But when it

comes to SEER vs EER, there are some very specific instances in which to

use each. Both SEER and EER are measurements of an air conditioner’s

energy efficiency and are given as a value ranging from around 8 (such as

SEER-8) and 30 (such as EER-16). The higher an air conditioner’s SEER or

EER rating is then the more energy efficient the unit. In this article, we will

explain what SEER is, what EER is, and finally when to use SEER vs EER.

Before Discussing SEER vs EER, We FirstNeed to Ask What is SEER, and What is EER? What is SEER?

Before tackling SEER vs EER lets take a look at each individually, starting

with SEER. SEER stands for Seasonal Energy Efficiency Ratio and is the

most common way to evaluate an air conditioner’s efficiency. Now it is

important to understand that this is only a measure of cooling power, and

applies to air conditioning. An air conditioner’s SEER rating is

the ratio of the cooling output of an HVAC unit

over a typical cooling season (measured in British Thermal Units, or BTUs),

divided by the energy consumed in Watt-Hours. It is the averageover a cooling

season, and is calculated using a constant indoor temperature and varying

outdoor temperatures ranging from the 60’s to over 100 degrees. SEER also

uses average US household energy expenditures in its calculation. A unit’s

SEER value is displayed on its Energy Guide Tag (left) as a number ranging

from around 8 to 30, although right now there are few air conditioning units

more efficient than about SEER-23. So for instance, an air conditioner with a

value of SEER-23 will be far more efficient than a unit with a rating of SEER-

14.

For more about SEER, check out Wiki: Seasonal Energy Efficiency Ratio.

Do You Live in Santa Clarita, California or Seattle, Washington? The Problem With SEER. SEER can, however, be misleading. What people often don’t realize is that

SEER is a ratio that only applies to a very specific set of test perimeters which

cover a pre-set temperature range. The problem with this is that when SEER

is calculated it is calculated across the same universal range, regardless of

where the person who is purchasing the air conditioner lives. Ask yourself,

when was the last time that it was 65 degrees in the summer if you live in

Santa Clarita, California? Probably a lot less likely than if you live in Lake

Arrowhead or worse yet, Seattle, Washington. So although SEER is a

universal measure of efficiency, it can be misleading in the sense that the

average temperature range in Santa Clarita is far different from the average

summer temperatures in Bozeman, Montana, but yet the same SEER rating

would be on the tag in each.

How to Calculate Your Equivalent SEER Rating for Your Climate Zone.

As a guideline, SEER is calculated across a wide temperature range but the

average of that range is about 83 degrees. If 83 degrees is the average

summer temperature for your area, then an AC unit’s SEER value is spot on

for your home (and I envy you). If your area is hotter, however, then subtract

2 points from a unit’s SEER rating for every ten degrees above 83 that is the

average temperature for your area. For instance, in Santa Clarita an average

summer temperature might be 93 degrees. This would mean that an HVAC

unit with a SEER rating of SEER-14 would have an equivalent rating of SEER-

12 in Santa Clarita.

93 – 83 = 10

+10 = 2 SEER points

SEER-14 rating – 2 SEER points = SEER-12 rating, or the equivalent SEER

rating calculated for your climate area.

How Important is SEER Rating?

After calculating the equivalent SEER rating for your area, you can take a look

at how much energy a high SEER rating can save you:

As you can see, paying for an air

conditioner with a SEER value of SEER-23 over the lifetime of the unit will

save you about $8,500 in electricity costs over the lifetime of your unit as

compared to an older unit that has a rating of SEER-8. Since 2006, the

Federal Government requires a minimum SEER rating of SEER-13 for all new

air conditioners, but an older AC might be lower. Lennox has a useful

calculator that will tell you how much money you can save by upgrading to a

newer air conditioner from an older SEER-10 unit. This calculator is only an

estimate, of course, and one thing I don’t like about it is that you can’t enter in

a starting SEER value – it instead assumes that your start value is SEER-

10. Just enter in the new SEER value and it will calculate your 5, 10 and 15-

year energy-expense savings:

Lennox SEER Energy Calculator.

For more information on how to lower your air conditioning costs, try:

How to Lower Your Electric Bill in the Summer.

What is EER?

Again, before tackling the question of when you should use SEER or EER,

you need to know what each of them is. EER stands for Energy Efficiency

Ratio, and is actually an older means of calculating energy efficiency than

SEER, having been used since 1975. Like SEER, an air conditioner’s EER

rating is a means of measuring an air conditioner’s efficiency, but where SEER

is a means of measuring seasonal efficiency ratings, an HVAC system’s EER

is more of a constant. Simply put, EER is more of an engineering number,

than a marketing number, and will probably be used by an HVAC

technician. EER values are also often encountered when looking at smaller

window AC units for which calculating a SEER value would be

impractical. EER is calculated using a constant outside temperature of 95

degrees, a constant inside temperature of 80 degrees and a humidity level of

50%. No seasonal temperature changes are factored into a unit’s EER rating.

The Advantages of an Air Conditioner’s EER Rating.

If you read the section on a unit’s SEER value, then you know that SEER is a

good approximation of a unit’s efficiency if the average summer temperature

in your area is around 83 degrees, but can be misleading if you live in

Southern California or the South. Conversely, an EER value is an objective,

set standard that can be used to directly compare two air conditioning units

without worrying about the seasonal changes in your area. For instance, how

a SEER-21 rated air conditioner operates during the summer in Bozeman,

Montana is far different from how it will perform in a Santa Clarita summer. A

unit’s EER rating can also be used to directly compare a Carrier Infinity Series

air conditioner to a Lennox Signature Series, for instance, but in short, EER is

a more technical, objective means of rating an air conditioner’s efficiency.

Now that you know about energy ratings, you can start shopping for more

energy efficient air conditioners. For more information on the energy efficient

Carrier Infinity-21 Series or the Amana-18, check out:

Carrier Infinity vs Performance Series Air Conditioners.

and

Amana vs Goodman Air Conditioners.

When to Use SEER vs EER. So now that we know the differences between SEER vs EER, we can take a

look at when to use each. Like we discussed, SEER is a great way to get an

idea of how a unit operates throughout a cooling season, and a unit’s EER is

an objective way to measure an air conditioner’s efficiency, but here’s when

to use each:

When to Use SEER.

SEER is most common. SEER can be used to compare one AC unit to

another directlyand is most commonly encountered when looking at large,

central air conditioning units. However, it should not be used to measure how

efficiently your new air conditioner will operate or how much money you can

expect to save without making a calculation. This is because as discussed

above, a SEER rating is only a rating based on a standard test across a

specific seasonal temperature range. As such, use the calculation in the

SEER section above to first figure out what your equivalent SEER rating would

be for your climate zone, then make the best decision for your area. Once

you’ve found the equivalent SEER rating for your area, then you can easily

calculate your expected energy used and money saved.

When to Use EER.

EER ratings are more commonly encountered with smaller window mounted

air conditioners. An air conditioner’s EER rating is best used to

objectively compare air conditioners or to do any type of load or engineering

calculation. Because it is not diluted by additional inputs, the EER value, in

my opinion, is the most accurate way to compare two different HVAC units for

the purposes of using Manual-J Load Calculations.

Which is Better for a Homeowner,

SEER or EER? To be perfectly honest, it can be hard to even find a central air conditioner’s

EER value without digging into some manuals. Most of the time, EER is used

on smaller, window air conditioners where using SEER would be

impractical. Some manufacturers will note it, but it is used far less frequently

than a SEER value.

In general, if you are a homeowner then I would use the SEER value as a

means of comparing units to one another, and I’d use a unit’s EER value if

you are looking at a window AC unit or if you are an HVAC contractor doing a

Manual-J calculation. Entering in a SEER value in a Manual-J can be done,

but ensure that you take into account the average temperatures for your area.

Final SEER vs EER Tip: At the end of the day, SEER and EER can be very useful for comparing

different air conditioning units to one another, but are not the end of the road

to increasing efficiency and decreasing energy costs. More importantly than

SEER or EER would be an HVAC unit’s size, and whether it is the proper size

for your house. If you pay the money for a SEER-23 unit but that unit is too

big for your house, then it will not run as efficiently as it should, so I’d check

out: