EER Rating Explained: Learn What Is Good for HVAC Systems

Have you ever considered how efficient your current cooling or heating system is?

Standalone ACs and Whole house HVAC systems consume a lot of electricity, leading to high energy bills.

Therefore, it’s imperative to consider the EER ratings of an air conditioning system when purchasing. But what are EER ratings exactly? Read on as we elaborate:

What Is EER Rating?

The Energy Efficiency Ratio (EER), also known as Energy Efficiency Rating, is the energy performance value employed by HVAC systems to identify the cooling power (in BTU/hour) of an AC unit in a given electrical power (measures in wattages).

You can find it on the yellow and black ‘energy guide’ sticker inside the condenser.

In short, EER is a useful way to find out how effectively and efficiently your HVAC system functions. For instance, a 120,00BTU AC unit, which uses about 1200watts, has a 10 EER rating.

The greater the EER rating, the more effective and efficient your HVAC system is. An efficient cooling/heating system will decrease operating costs and maintain a comfortable and consistent indoor temperature.

Senville SENL-09CD Energy Guide

What Is Considered A Good EER Rating?

A unit with an 8.5 EER rating is usually considered an average energy-efficient unit. For example, anything lower than this is deemed to be a below-average energy performance unit.

This is because they consume more power than 8.5 EER units and therefore aren’t advisable for a purchase.

However, all units with EER ratings above 8.5 are termed as good air conditioners. Units with 11.5 or 12 EER ratings are considered the most efficient AC units on the market.

Benefits Of High EER Ratings

Here are a few benefits of a high-rated EER AC unit:

  • Lower Electricity Bills:
    An HVAC system with excellent EER/SEER ratings consumes low energy and provides savings on energy bills. If you switch from your old 8 EER/SEER rating unit to a 16 SEER/EER rating unit, you can save up to 50% on utility bills.
  • Better Cooling Power:
    Generally speaking, all air conditioners with a higher EER rating also come with better accompanying features. These features will result in better cooling and start-up time. This means that you will save money and also benefit from a unit that cools better.
  • Lower Life Cycle Cost:
    Although it’s a fact that air conditioning units with higher EER/SEER ratings are expensive to install, however, they are less costly to operate compared to other HVAC systems. In addition to that, a better AC unit will incorporate superior tech and therefore be less vulnerable to malfunctions.
  • Low Carbon Footprint:
    Since high-efficiency air conditioning units consume less energy, they have a smaller carbon footprint; in other words, they don’t contribute as much to greenhouse gas emissions. Less energy used means fewer fossil-fuels burned. It’s good for the wallet and the environment. Window ACs are generally smaller than most other models.
seer rating chart

How To Calculate EER Ratings For Your AC

Calculating the Energy Efficiency Ratio (EER) of an AC unit is quite simple. All you have to know are two metrics:

  1. The capacity of your air conditioning system. For example, 6000, 10000, 12000, and 18000 BTUs
  2. Power of your AC unit. For instance, 800, 1200, and 1400 wattages.

To get EER ratings, you have to divide the unit’s cooling capacity by the power. Here’s the equation:

Energy Efficiency Ratio (EER) = Cooling capacity (BTU) / Power (Watts)

Let’s suppose we have a mini-split AC unit with a 12,000BTU cooling capacity, which uses 1000 watts of power. Put that into the EER equation.

EER rating = 12000BTUs / 1000watts

EER rating = 12

The 12 EER rating means every 1 watt of power that we give to the unit; it will provide us with a 12BTU cooling effect.

This is far better than, for example, 12,000BTU and 1400watts air conditioner. In this instance, the EER rating would be:

EER rating = 12000 BTUs / 1400 watts = 8.5

Here, it means for every 1 watt of power, the AC unit will provide you with a mere 8.5 BTU cooling effect.

Judging by the EER ratings of both these units, the air conditioner with an EER rating of 12 is 40% more energy-efficient than the one with an 8.5 EER rating.

However, one thing to consider is that EER is dependent on specific environmental conditions:

  • 95°F external temperature
  • 80°F internal temperature
  • 50% relative humidity

EER Vs. SEER: What’s The Difference

When searching for an ideal air conditioning system for your house, you’ll come across two types of ratings: Energy Efficiency Ratio (EER) and Seasonal Energy Efficiency Ratio (SEER).

As described above, EER rating is the standardized measurement of your units’ energy efficiency and is usually used for room ACs.

On the other hand, SEER measures the efficiency of your unit throughout the season. Unlike EER, it is calculated and tested against various external temperatures ranging between 65 to 107°F.

These ratings are used explicitly for centralized air conditioning systems.

In short, the SEER rating is an average energy-efficiency rating of a unit, while EER denotes energy-efficiency during a specific period only.

Molekule Air Mini Purifier in Office

Quick Guide To Converting AC’s Efficiency

EER To SEER Conversion

Both SEER and EER ratings measure your HVAC appliances’ energy efficiency and devices such as heat pumps and, of course, air conditioning systems.

Therefore, if you want to convert EER ratings to SEER ratings, use the following universal formula:

EER = 0.875 x SEER

SEER = EER / 0.875

EER To KW Ton Conversion

KW/ton is another crucial metric employed to measure a unit’s efficiency. It’s widely used for large industrial and commercial air conditioning systems. The lower the KW/ton, the more effective and efficient it is.

Here’s a formula you can use to convert EER rating to KW/ton:

EER = 12/ KW/ton

KW/ton = 12 / EER


COP or Coefficient is another metric used to measure the energy efficiency of cooling and heating devices.

To convert EER rating to COP, use the following equation:

EER = 3.41 x COP

COP = EER / 3.41

Put the EER value in the above equation, and you’ll get a COP rating.

People Also Ask (FAQ)

What Are Some Other Ways To Maximize HVAC Energy Efficiency?

Ensure the thermostat is exact at 78°F and utilize ceiling fans whenever necessary to minimize room temperature; you can also install an automatic thermostat. Furthermore, always keep televisions, computers, and lamps away from the thermostat and conduct consistent HVAC inspections.

What Is A Good EER Rating For A Portable Air Conditioner?

Anything beyond nine is considered a good EER rating for a portable air conditioning unit.

Does EER Include Fan Energy?

Yes, the EER ratings of HVAC systems do include fan energy as well.

How Many Hours A Day Should An AC Run In Summer?

Though it varies according to air conditioner types and models, your AC should run nine hours a day during summers on average.

How Much Does It Cost To Run A Portable AC All Day?

On average, a portable air conditioner unit may cost you between $0.06 to $0.8/hour. If you use it 9 hours per day, it would cost you anywhere between $0.54 to $7.2 and $1,944 per month.

Why Is My AC Not Removing Humidity?

The thermostat fan could be set to ‘on’ rather than ‘auto, or you may have dirty evaporator coils. Improper installation could also lead to a refrigerant leak or leaky ductwork. Another reason could be that you have an oversized HVAC system.


Knowing the energy efficiency ratings of air conditioners is essential if you want to ensure optimal cooling while keeping the utility bills low.

Various air conditioning systems provide different energy efficiency ratings; however, keep in mind that the higher the EER rating, the better and more efficient a unit is.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.