Energy Efficiency Ratios: SEER vs EER?

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Energy Efficiency Ratio: SEER vs EER

“Going green” is a common principle that people stand by today.

People are more often factoring in the effect that their life style has on the global environment and trying to live whilst leaving as little a carbon footprint as possible to benefit the Earth.

This only stands to benefit the homeowner too, as it involves using less energy to run their household appliances and electrical goods without sacrificing performance. It means having less of an impact on the utility bills.

It turns out that achieving energy efficiency is a win-win situation, if you can achieve a balance between the amount you spend on the appliance, and the amount you save from using it over the years.

HVAC systems are no different and when it comes to purchasing a new tankless water heater, air conditioner or heat pump, you will often find the performance of these units in AFUE, EER or SEER displayed on its energy guide label. But what do they mean to you?

EER and SEER are both used to describe the efficiency of cooling units while on the other hand, AFUE and HSPF is for heating. We’ll take a look at cooling for now but check out our AFUE and HSPF guide for heating efficiency information.

By definition, the energy efficiency ratio is a measurement of the output of your HVAC unit, measured in BTUs (British Thermal Units) in relation to the amount of power it consumes.

The energy efficiency of an appliance in relation to another can be compared by the amount of power that’s consumed to achieve the same BTU output.

 Have a look at this straight forward air conditioner example:

  • Air Conditioner A: Outputs 12,000 BTUs / Consumes 800 Watts
  • Air Conditioner B: Outputs 12,000 BTUs / Consumes 500 Watts

By this we can see that air conditioner B is more energy efficient than air conditioner A as less energy is consumed by the unit to produce the same BTU output. This boils down to you spending less on utility bills, to keep your living room comfortably cool during the summer.

That’s the basic principle behind energy efficiency but what are the specifics? What is EER? What is SEER? How are they relevant? And how is EER and SEER different?

In this article I am going to tackle these questions to give you a better understanding of energy efficiency ratings so that you can join the SEER vs EER debate, go on to compare HVAC units and know for yourself which is going to cost you less in the long run.

What is EER?

In case you missed it, EER stands for Energy Efficiency Ratio or Energy Efficiency Rating and it is a means of calculating the energy efficiency of a particular appliance. The EER is expressed in numerical values and calculated by dividing the output (BTUs) by the energy consumption (Watts).

The higher the EER value, the more energy efficient the unit is.

The Energy Efficiency Ratio Formula is as follows:

BTU Output

Watts Input = EER

Going back to our air conditioner example with air conditioner A and air conditioner B:

  • The EER of air conditioner A would be 15 (12,000 / 800)
  • The EER of air conditioner B would be 24 (12,000 / 500)
Energy Efficient Air Conditioner

And so air conditioner B has a significantly higher EER than A meaning that it would make less of an impact on your utility bills and require less electricity consumption to produce the same BTU output.

With that being said, this would mean air conditioner B would cost more upfront, but will be more efficient and save more in utility bills over time.

The energy efficiency ratio formula has been in use since 1975, making quite a bit older than SEER. EER is not used as commonly as SEER either, it’s more of an HVAC technician’s tool to measure the overall performance of the unit. It can also be converted to COP to show its power efficiency.

It is however, more commonly used for small window air conditioners as SEER would be less effective in this case.

What is a Good EER Rating?

A good EER rating is the highest value compared to other units of the same BTU value. If you are looking at an air conditioner with an EER of 14 and another one with an EER of 12 that both have the same BTU output, the first one is more energy efficient.

With this considered, you will find AC units that are more efficient with lower BTU outputs and some more efficient with high BTU outputs. So a good EER rating will really depend on the BTU output range you require to cool the area you desire.

What is SEER?

SEER stands for Seasonal Energy Efficiency Ratio or Seasonal Energy Efficiency Rating and differs from EER because it takes into account the seasonal change in climate. It does not apply to heating and is only a measurement of the cooling power of a cooling unit such as an air conditioner or a heat pump.

It doesn’t just measure the energy efficiency of the unit, but measures its energy efficiency over the course of a cooling season based on a constant indoor temperature and varying outdoor temperatures between 60 and over 100 degrees Fahrenheit.

The equation to measure SEER can be quite complicated, but it can be used to predict the amount you would spend on energy bills to run the unit.

In general, the conditional temperatures that the cooling unit is tested under is a universal temperature range with an average of 83 degrees Fahrenheit. Even though it is taking temperature fluctuations throughout a season into account, it can be seen as a flawed test because seasonal temperatures can differ depending on where you live.

In other words, if your average summer temperature does happen to be 83 degrees Fahrenheit, then the SEER rating would be accurate. Otherwise you would need to calculate an equivalent SEER value to your climate zone.

To do this, you simply subtract 2 SEER points for every 10 degrees over 83 degrees in average summer temperature.

 For Example:

Say you live in Dallas with an average summer temperature of 96 degrees.
You have a unit with SEER value of 12.
You would subtract 2 to have a local equivalent of 10.

What is a Good SEER Rating?

The SEER values that are shown on your HVAC unit are a minimum and a maximum value. The minimum value of modern AC units is typically SEER 13 or 14 but this does depend on requirements set by your particular state.
The maximum value can go up to around 30 SEER and this is an indication of the capacity of the technology used in the unit.

This doesn’t mean that the unit will constantly be running at 30 SEER, but it changes with the fluctuation of outdoor and indoor temperatures.

It also doesn’t mean that the highest SEER rating is best for you, your home and your wallet and that is because most people do not need the highest SEER value!

In fact, they often end up spending more on the high SEER unit, all the installation costs and potentially the ducting than they save in utility bills over the span 10 to 15 years. And that’s not even taking into account any maintenance or repair costs.

Finding out what is the best SEER value is tricky because there are many variables which are taken into account when SEER is measured. There are also all the variables of your home to take into account too. Your location, the size of your home, the cost of electricity in your state, and even attitude as these go into the size of the unit you’ll need.

In all honesty, it’s usually best to shoot for a standard SEER 14 or SEER 16 unit, as they are plenty efficient by comparison to the older AC models (SEER 8 – 10). They don’t cost anywhere near as much as the expensive SEER 25 units, which really would not have you saving much on bills for the amount you pay upfront.

When to Use SEER vs EER

Air Conditioning Unit

Now that you know the difference between both means of measuring energy efficiency when it comes to cooling units, you may be wondering which is best to go by.

The SEER measures how effective the unit is throughout the season you would use the cooler, taking into account changes in temperature. The EER on the other hand, gives you an idea of the overall efficiency of a unit.

When shopping for a new heat pump or air conditioner, you should only compare the units by EER or SEER values. Don’t compare the EER of one unit to the SEER of another, it wouldn’t make sense to as they are not directly equivalent to one another. And this is why:

When to use SEER

SEER is most commonly used to compare large, central air conditioning units and will give you a good idea of how high performance a unit is in comparison to another for your local area. It’s actually a fantastic indicator of this.

You would use SEER to calculate your local SEER equivalent as we discussed above, and use this to compare how well the unit will work for you in comparison to the SEER value of others.

If you need help calculating your savings based on SEER rating, you could take a look at this useful SEER calculator provided by Lennox.

When to use EER

Since the EER is more often used by HVAC contractors, it is not as useful to homeowners. While it does tell you the efficiency rating of the unit, it doesn’t take into account how much you are likely to use the device based on seasonal changes in climate.

It does however, give you a good idea on the energy consumption of the unit and is much more accurate than SEER for comparing the general efficiency of two units. EER is more accurate for those who live in the southern states, which get the luxury of continual hot temperatures all year round.

SEER vs EER: Which is Better?

While there is no doubt that EER can give a much more accurate and standardized measurement which can easily be used in calculations, it is only useful for HVAC professionals.

Or those that live in arid climates with no worries about variations of outdoor temperatures throughout the year.

But for homeowners and those that live in temperate climates, SEER is by far more useful. It allows you to compare cooling units directly and you can also calculate the energy cost of any particular unit too!

You can easily compare the given SEER rating of cooling systems while simultaneously compare their price, their size so that you can assess which would suit your home and your wallet with that information combined.

Using Energy Efficiency Ratios as a Buying Factor

Even though the EER and SEER are useful pieces of information to have when considering your next HVAC purchase, they are not the be-all and end-all when it comes to choosing the right unit for you.

There’s other considerations you need to take into account to get good value for your money, depending on the type of cooling unit you are looking for.

When it comes to sliding window air conditioners, you’ll want to also think about the size of the unit, its cooling capacity, cost of the unit, quality of its construction, quality of its components and even how easy it is to access to clean the coils.

A heat pump on the other hand, will have some similar factors to consider but you’ll also want to think about installation costs, whether they are right for your location, ductless or ducted, and other features that may be of use.

So don’t just go by the EER and SEER ratings, make sure you do all the research and know what you need before you compare the energy efficiency ratings of the units in the range that you require.

About the Author

Dave Miller is a HVAC technician with over 10 years in the industry. Dave created HeatTalk with the ambition for it to become a resource for individuals looking for answers, whether they be a layman, student or a professional.

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