EER Rating Explained: What’s The Best EER Rating for Your AC?

EER Rating Explained

An energy-efficient HVAC product saves dollars and performs for longer years. If you are browsing to buy a new air conditioner unit and wonder how to check its efficiency to make the final decision, this article is just for you.

We all want ways to cut down utility bills and look for air conditioners that consume less energy and perform at optimum capacity. A quality air conditioner might come with a higher upfront cost.

But if you compare lifetime (generally twelve-fifteen years) consumption of electricity and minimum technician call, the high cost will be compensated nicely.

HVAC product manufacturers produce energy-efficient air conditioners to tap the high demand for such machines. Air conditioners come with EER and SEER ratings as the measurement of efficiency.

In this passage, we will explain EER and ways to understand good EER ratings for air conditioners.

What Is The Energy Efficiency Ratio?

HVAC manufacturers have been using Energy Efficiency Ratio or EER since the mid-70s. EER measures the air conditioner’s energy efficiency through constant inside and outside temperature.

A higher EER rating means your air conditioner is designed to provide the optimum level of cooling per Watt of energy available at home. 

EER is a rating given for energy performance for cooling devices. Look out for the ratings on your AC specification sheet. Comparing energy efficiency is essential while browsing for an ideal air conditioner for the home. 

What Is A Good EER Rating for Air Conditioner?

According to AC experts, EER ratings 8.5 and above are considered good ratings. Also, search for Energy Star certification. Energy Star assures green practices in the production and supply chain.

It can also increase operational efficiency and save up to ten percent of the power consumption. Look for higher EER ratings because, in AC, the higher is, the better.


Suppose you own an air conditioner with 10,000 BTU capacity, and EER ratings are 8.5. It means the unit requires 850 Watt of energy to give us 10,000 BTU of cooling effect.

*In the next section, we will discuss a calculation of EER and good EER ratings for different categories of AC.

How To Measure EER Ratings of an Air Conditioner?

To calculate EER, you need to know your HVAC equipment’s capacity and energy requirements. Capacity can denote as 6,000 BTU, 10,000 BTU, 12,000 BTU etc., and Energy can be written as 800W, 1,000W, 1,200W etc.

The formula for EER Measurement

Capacity in British Thermal Unit (BTU/hour)/Power (Watts)=EER Ratings

Let’s explain the formula with the help of an example:

A mini-split AC with 10,000 BTU capacity and powered by 1000W electricity. Apply for the numbers, and let’s derive the EER for the unit.

EER Ratings: 10,000 BTU/900W= 11.11

Here 11.11 EER rating means the mini split air conditioner will provide an 11.11 BTU equivalent cooling effect for every 1W of energy consumed.


There are multiple types of air conditioners available in the market. They perform differently according to local conditions, climate, and other factors. To cover all types of units, SEER and CEER metrics were introduced along with EER. SEER is generally used for central air conditioners, CEER for window air conditioners, and EER for room air conditioners.

What Is a Good EER Rating for Air Conditioner Unit?

Energy efficiency varies for different types of air conditioners. Multiple factors affect performance during high Summer and cold Winter. EER requires when you browse for room air conditioners mainly. Portable AC can be easily moved from one place to other and is flexible in use.

The advisable EER rating for room AC units is about 8.5. You can also understand 8.5 as the middle point, higher is a good option, and lower is not a good option.

Expert says 11.2 EER ratings with Whynter dual-hose is the most reliable air conditioner for optimum energy efficiency and significant power savings.

Theoretical Maximum EER

We can also use the first law of thermodynamics apart from the aforementioned method to calculate AC efficiency. Theoretical EER measures efficiency through Coefficient of Performance (COP). COP is a criterion to estimate the performance of cooling and heating devices.

The COP Equation: COP = Tcold / (Thot – Tcold)

EER = 3.41 x COP

In this equation, T(hot) stands for hot outside temperature in Summers, and T(cold) refers to the desired temperature from the air conditioner at home. 

Example to Explain the Formula

Let’s consider a scorching summer day with outdoor temperature 85F {T(hot)=302K} and desired indoor temperature 70F {T(cold)=294K}. Now apply the on the mentioned formula. We will have to plug the temperature in degrees Celsius in the upper equation to get the theoretical maximum EER rating.

EER: 3.41x294K/(302K-294K) = 125.31


We hope this analysis will help calculate and understand the EER for the air conditioner at home. Get the best AC after considering ideal EER, energy savings, and accumulated profit on utility bills over the machine’s lifetime.

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