What Is an EER Rating? (EER vs. SEER)

airmax charleston what is an eer rating min 1

EER vs. SEER Ratings, What’s the Difference?

If you are in the market to buy and install an air conditioning unit, you may be surprised to see all the options available. It is not as simple as picking the AC unit that looks best, but it requires a detailed investigation to get the best system. You have to consider the various types, and then you have to look into the different sizes. 

You have no doubt come across the terms “EER” and “SEER”. You may have seen them while browsing for a suitable AC system. What do they mean, and how do they affect your decision? Read on to find out how you can use these terms to install the perfect AC unit.

A room air conditioner’s efficiency is measured by the energy efficiency ratio (EER). The EER is the ratio of the cooling capacity (in British thermal units [Btu] per hour) to the power input (in watts). The higher the EER rating, the more efficient the air conditioner. National appliance standards require room air conditioners to have an energy efficiency ratio (EER) ranging from 8.0–to 9.8 or greater, depending on the type and capacity, and ENERGY STAR® qualified room air conditioners have even higher EER ratings.

The Association of Home Appliance Manufacturers reports that the average EER of room air conditioners rose 47% from 1972 to 1991. If you own a 1970s-vintage room air conditioner with an EER of 5 and you replace it with a new one with an EER of 10, you will cut your air conditioning energy costs in half and hopefully prevent future ac service calls.

When buying a new room air conditioner, look for units with an EER of 10.0 or above. Check the EnergyGuide label for the unit, and also look for room air conditioners with the ENERGY STAR label.

EER vs. SEER: The Differences


The standard way to measure an air conditioner’s efficiency is by using the Energy Efficiency Ratio, also known as EER. In other words, it is the ratio of an AC unit’s cooling capacity to the power inputs. The ideal ratio will have a higher cooling capacity compared to the power inputs. The higher the EER rating, the more efficient your AC unit is.

National standards require that your AC units have an EER rating between 8 and 29. If it has a rating higher than this, it’s even better. ENERGY STAR AC units will have even higher EER ratings than ordinary ones. 

As time goes on, AC unit production companies strive to make their products even more energy-efficient. An AC unit made in the 1970s can be up to 47% less energy-efficient than an AC unit produced in the 1990s. You may love your old air conditioner, but you probably don’t love the electricity bills. 

For example, if you increase the EER rating of your AC unit from 5 to 10, you could almost cut your electricity bill in half.


Now that we’ve discussed the EER rating, let us discuss the SEER rating. SEER stands for Seasonal Energy Efficiency Ratio. This is the same as an EER rating in that it measures the ratio of the cooling output compared to the power input. However, it takes into consideration the typical cooling season. This ratio is a maximum efficiency ratio, much like the miles per gallon ratio for your car. This means that your energy efficiency is not constant and can increase or decrease depending on certain conditions. 

The minimum SEER rating is 13. Most modern air conditioning companies produce units that have a rating between 13 and 22. However, this is only a maximum. There are factors that can decrease the energy efficiency of your air conditioning units.

Sizing and Selecting A Room Air Conditioner

The required cooling capacity for a room air conditioner depends on the size of the room being cooled — room air conditioners generally have cooling capacities that range from 5,500 Btu per hour to 14,000 Btu per hour. A common rating term for air conditioning size is the “ton,” which is 12,000 Btu per hour.

Proper sizing is very important for efficient air conditioning and fewer ac service calls. A bigger unit is not necessarily better because a unit that is too large will not cool an area uniformly. The oversized unit will also cool the room to its thermostat set point and shut down prior to properly dehumidifying the room, leaving the area feeling damp or “clammy.” A small unit running for an extended period operates more efficiently and is more effective at dehumidifying than a large unit that cycles on and off too frequently.

Based on size alone, an air conditioner generally needs 20 Btu for each square foot of living space. Other important factors to consider when selecting an air conditioner are room height, local climate, shading, and window size.

Verify that your home’s electrical system can meet the unit’s power requirements. Room units operate on 115-volt or 230-volt circuits. The standard household receptacle is a connection for a 115-volt branch circuit. Large room units rated at 115 volts may require a dedicated circuit and room units rated at 230 volts may require a special circuit.

If you are mounting your air conditioner near the corner of a room, look for a unit that can direct its airflow in the desired direction for your room layout. If you need to mount the air conditioner at the narrow end of a long room, then look for a fan control known as “Power Thrust” or “Super Thrust” that sends the cooled air farther into the room. If you need assistance in mounting your room air conditioner, you may need to schedule an ac service.

Other features to look for include:

  • A filter that slides out easily for regular cleaning
  • Logically arranged controls
  • A digital readout for the thermostat setting
  • A built-in timer.

How to Keep Stay Energy-Efficient

So now you have an AC unit that is highly energy-efficient, what’s the next thing to do to keep your bills down? Well, there are other things you can do to use less energy, as there are many factors that will influence the amount of energy your HVAC unit uses. 

Choose the Right Size AC Unit

An AC unit that is too small will struggle to cool your home efficiently. It may feel like your house is never cool enough while your electricity bill skyrockets, even though you bought an AC unit with a high SEER or EER rating. An AC unit that is too big will cool your room down to the temperature on the thermostat and then shut off. This may not have been enough time to dehumidify the house, leaving you with damp or sticky indoor air. 

So, when selecting your ideal AC unit, be sure to ask the advice of a professional HVAC technician. They will use the square footage of your home to calculate the correct tonnage you need. 

Sufficient Voltage

It’s important to ensure that your electrical system can meet your AC unit power requirements. This will require a professional to inspect. If your home cannot apply sufficient voltage, you may need a special circuit rated at 230 volts so you can operate your energy-efficient AC unit. 


If your home is poorly insulated, it will be difficult to maintain the temperature inside. Your AC unit will have to run cooling cycles more often to keep your home at the temperature on the thermostat setting. To combat this, you may need a bigger AC unit, or you could insulate your home properly. Before making a decision, speak to an HVAC specialist and see what they recommend. 

The Benefits of a High SEER and EER Rating

You should also know that as the SEER and EER rating increases, so does the price of your air conditioning system. This might scare you into opting for a lower energy-efficiency rated unit. Here are two great reasons to pick a higher SEER rating. 

Lower Monthly Electricity Bills

This is a benefit that we have frequently mentioned. You can save money every month just by having a better AC unit. 

Reduce Your Carbon Emissions

If you are concerned about the state of our planet, you can rest easy by knowing that you have chosen the most energy-efficient option on the market. We have to protect the planet by means necessary. Installing an eco-friendly air conditioning unit may seem like no big deal, but every little bit of energy saved counts. 

If you would like the best air conditioning unit for you and your family, we are proud to offer to finance your AC installation. You can have your dream AC unit now and pay it off. Contact us today to see if you qualify!

Charleston’s #1 Most Reliable HVAC Company

Choosing an AC unit is not as simple as it sounds, as you can see. It requires some research. If this overwhelms you or you do not have enough time to go through the process of choosing an AC unit, contact Max’s Fix-it 24/7 Heating & Air. We have a team of trained HVAC technicians that already have pre-existing knowledge of the AC units on the market. They also have a pretty good idea of what AC unit will be right for your home. 

Save time and money by contacting Max’s Fix-it 24/7 Heating & Air today. We promise that you won’t be sorry.


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