What is the Most Efficient Window AC in 2024 (670 Units Studied)

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EER rating is the energy efficiency ratio of an air conditioner.

Energy efficient window air conditioners are 9.1 EER to more than 15 EER, with 15.7 as the current highest EER. Most Energy Star window ACs have EER ratings above 10.

Discover high efficiency window AC brands, models and efficiency ratings plus how to cut energy costs on this page.

High Energy Costs and Demand for Energy Efficient Window ACs

Electricity costs have risen 64% since 2000 and, according to the US Consumer Price Index, 15.2% in a recent 12-month period.

In 1993, air conditioning accounted for just 4.6% of electricity use, the average is now over 12% according to the US Energy Information Administration

High Energy Costs and Demand for Energy Efficient Window ACs

And who pays the most for electricity? Homeowners do – a current average of 13.7 cents per kWh for residential customers while commercial customers are paying 11.3 cents/kWhaccording to the US Energy Information Agency.

With that information in mind, let’s explore what is available in the energy efficient window air conditioner market.

How Window AC Efficiency is Measured: CEER vs EER

Since 2014, all window ACs have CEER ratings, and most are still rated with EER too.

EER is the energy efficiency rating. According to General Electric, “EER is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level. The higher the EER, the more efficient the system. It is calculated by dividing the cooling capacity in BTUs per hour (BTUH) by the power input in watts. EER is expressed as BTUH/watts.”

CEER is the rating that takes into account the fact that the unit uses a small amount of energy when plugged in but not running. The energy used is called standby wattage, and it is wasted energy.  

In a nutshell, the CEER rating of any window air conditioner is typically the same or about 0.1 lower than its EER rating, so it makes little difference. 

Since most consumers are more familiar with EER than with CEER, we use EER in the following sections when describing the efficiency rating of a window AC. 

How Many EER are High Efficiency and Most Efficient Window ACs?  

The EER of Energy Star Certified Window ACs ranges

The EER of Energy Star Certified Window ACs ranges from 9.1 to 15.7, while the average is 11.7. (based on 670 Units studied)

High Efficiency Window AC Units have a listed 12 EER or more, and 57.3% of window ACs have EER ratings of at least 12 EER.

Based on Energy Star requirements, the most efficient air conditioner should have at least 13.8 EER. Only 6% window units from 6 brands (GE Profile, LG, Frigidaire, Midea, Danby and Dreo) meet this standard. 

The highest EER for window ac is 15.7. 

Energy Star Window AC Efficiency Requirements

To be Energy Star certified, the unit must be at least 10% more efficient than the minimum government standard. There is a range of efficiency levels that qualify. For example, in 12,000 BTU capacity, certified Energy Star ACs range from 9.1 for 35,000 BTU models to 15.7 for the 10,000 BTU unit listed above.

The current Energy Star minimum standard is 9.9 CEER for 28,000 BTU ACs and 12.1 CEER for 6,000 BTU models. Other popular sizes have requirements between 9.9 and 12.1 CEER.

Tip: When a window AC has a standard compressor (not variable speed), the larger the unit, the less efficient it will be. That’s why Energy Star has a graded efficiency scale based on the size of the air conditioner.

High Efficiency Window AC Brands

As you shop for energy efficient window ACs, you will probably notice that some brands seem highly motivated to provide consumers with high EER window air conditioners.

In the Energy Star Certified Room AC list, here are the brands with the most models that meet the window AC efficiency requirements.

High Efficiency Window AC Brands
BrandEnergy Star Models
Perfect Aire36

As you can see, the brands with the most energy efficient window air conditioner models include Midea, GE, Frigidaire, Emerson’s Quiet Kool brand, TCL – a brand that isn’t as well known, and Gree.

Midea produces more than 100 different models that qualify for the Energy Star label. Several of them achieve EER ratings of 15 or higher, though the average efficiency for Midea is 11.3 to 12.0. General Electric, commonly called GE, also offers a good selection of high efficiency window air conditioners in sizes from about 6,000 to 25,000 BTU. The GE Profile units with 15.7 EER are the most energy efficient window ACs available today. Most high-efficiency GE models have EER ratings in the mid 11s. 

Most Efficient Window Air Conditioner Models by Size

What size window AC do you need?

This table shows common sizes, the highest EER rating and a few of the most efficient models.

Most Efficient Window AC By Size

Window AC SizeHighest CEER RatingMost Efficient Brands
5000 BTU12.1Keystone, Midea, Gree, Frigidaire, Perfect Aire
6000 BTU12.4LG
8000 BTU15.5LG, Comfort Aire, Danby, Emerson, Midea, Keystone, TCL
10,000 BTU15.7GE, LG, Midea, Danby, Frigidaire, Keystone
12,000 BTU15.4GE, Hisense, LG, Midea, MrCool
14,000 BTU14.7LG
15,000 BTU12.1Keystone
18,000 BTU14.7LG
20,000 BTU10.3Friedrich
22,000 BTU14.5LG
24,000 BTU14.3LG
25,000 BTU10.3Keystone, Koldfront, LG, Danby, Frigidaire
28,000 BTU9.9Friedrich
35,000 BTU9.1Friedrich

It used to be true, generally speaking, that the highest EER window air conditioners were the smaller ACs in the lineup. As size increased, efficiency would go down, as it does with central ACs. That’s still true for models that have standard compressors. The same level of efficiency can’t be achieved in a 24,000 BTU window AC, for example, that it can be in a 12,000 BTU model.

However, this isn’t true with window air conditioners fitted with a variable speed compressor. Size doesn’t affect efficiency at all in some units like the GE Profile Series – and only a small amount in other series with inverter-style, variable speed compressors. 

Highest EER Brands and Models

The highest EER window air conditioner is the 15.7 CEER units from General Electric, the GE Profile AHTR10AC and the GE Profile AHTR10ACH2. These are 10,000 BTU window ACs.

The LG LW8022IVSM is an 8,000 BTU AC with a CEER rating of 15.5. At 15.4 CEER are the GE Profile AHTR12AC and the GE Profile AHTR12ACH2, units identical to the two GE models above except that they are 12,000 BTU window air conditioners.

All of the highest EER window ACs have inverter-type compressors. The next section explains this technology.

BTUSq. Ft. CoverageMost Efficient (EER)

Here are the most energy efficient window air conditioners at the various sizes

  • 5,000 BTU: 12.1 CEER. Most brands make 12.1 CEER units. 
  • 6,000 BTU: 12.4 CEER. LG LW6019ER is this efficient. 
  • 8,000 BTU: 15.5 CEER. LG LW8022IVSM
  • 10,000 BTU: 15.7 CEER. GE Profile AHTR10AC and AHTR10ACH2
  • 12,000 BTU: 15.4 CEER. GE Profile AHTR12AC and AHTR12ACH2
  • 14,000 BTU: 14.7 CEER. LG LW1522IVSM and LW1517IVSM.
  • 15,000 BTU: 12.1 CEER. Keystone KSTAW15CE 
  • 18,000 BTU: 14.7 CEER. LG LW1817IVSM and LG LW1822IVSM
  • 20,000 BTU: 10.3 CEER. Friedrich 
  • 22,000 BTU: 14.5 CEER. LG LW2217IVSM 
  • 24,000 BTU: 14.3 CEER. LG LW2422IVSM (208V) and LG LW2422IVSM (230V) 
  • 25,000 BTU: 10.3 CEER. Keystone, Koldfront, LG, Danby, Frigidaire and Gree.
  • 28,000 BTU & 35,000 BTU: 9.1 to 9.9 CEER. Friedrich models KCL36A30A (28K BTU) and the two 35,000 BTU models KEL36A35A and KCL28A30A.

Inverter Compressors Is a Key Feature

This isn’t a technical article, so we won’t dwell on this. There are good articles available on the subject.

Basically, standard window air conditioners run at full capacity or “full blast” all the time that they are on. Some have a low and high stage, but very few. That’s not the same as low/medium/high fan speed.

Inverter compressors are also called variable capacity and variable speed compressors. They run more like cruise control. They speed up or slow down as needed to keep the room exactly the temperature you want. In very hot weather, they have to pump the refrigerant around faster to remove heat more quickly. In warm weather, they move more slowly – and more energy efficiently – and can still maintain the proper temperature.

The LG and GE models in the 14+ CEER and EER range achieve such high efficiency because of inverter compressor technology. In some cases, you will find in your research that CEER and EER ratings are the same for certain models. 

High Efficiency Window AC Cost

See the table for the cost of an Energy Star window air conditioner in popular size ranges.

Most Efficient Window Air Conditioner Cost 

BTUsCost Range
5000 – 6000$190 – $425
8000$285 – $475
10,000$340 – $550*
12,000$390 – $600*
14,000$415 – $645
15,000-18,000$500 – $950*
20,000 – 24000$640 – $1,000*
25,000 and Up$700 – $1,100

*Friedrich makes heat pump ACs costing more than $1,000

These are the MSRP, or Manufacturer Suggested Retail Price. You can almost always find a model for less online and at local home improvement stores and appliance sellers.

Price factors other than the efficiency level are features, WiFi, voice control and quality.

Is a High Efficiency Window AC Worth the Cost?

Yes, a high efficiency window air conditioner will repay the extra cost in 2-5 years depending on your climate.

The hotter your climate, the faster you will gain back the extra money you spend. Your energy bills will be lower every month. In fact, a variable capacity window air conditioner is at least twice as efficient as a standard window AC built 12-15 years ago.  

And if your goal is to reduce emissions, then of course the highest EER unit you can afford is the right choice.

Note: Friedrich Kuhl heat pump window ACs cost $1,000 to $1,500, and they are not worth the money. But if you want heat pump air conditioning and heating in a space, you might want to consider one vs installing a mini split system at twice the cost.

Pros and Cons of Highest EER Window ACs

It’s really all about cost.

You pay more for an energy efficient window air conditioner vs standard efficiency models. Expect prices to be $35 to $300 more per model, or about 10% to 25%.

That price difference doesn’t include the Friedrich Kuhl units mentioned above. They’re 2-4 times more expensive than most high efficiency window AC models.

And if you buy an AC with a variable speed compressor, repair costs will be higher if it breaks – or you might simply have to buy a new unit.

On the plus side, you will enjoy lower utility bills and energy consumption when cooling your room or home.

Does Outside Temperature Affect The Window Ac Efficiency?

Yes, the higher the outdoor temperature, the lower efficient the window ac is, the more electricity your window ac will consume.

Window ac typically runs at 64-109 F outdoor temperature, once the outdoor temperature is higher than 109 F, the efficiency will drop significantly and even can not function properly. 

What are the Most Efficient Portable Air Conditioners?

The most efficient portable air conditioner are models from Whynter, Danby and LG brands. Check the energy efficient portable ACs here.


Which window AC consumes less electricity?

ACs with variable speed compressors use less electricity than those with standard compressors. You can also check window ac watts here to calculate the electricity usage of your window ac.

What is the most energy efficient window air conditioner 2023?

15.7 CEER. GE Profile AHTR10AC and GE Profile AHTR10ACH2 window ACs are the most efficient for 2022. Their rating is 15.7 CEER, and they are 10,000 BTU.

How much does it cost to run a window AC?

Less than $70 per year. The US Department of Energy claims that Energy Star certified window air conditioners cost less than $70 per year to run – on average.

How much does a window AC cost to run a day?

Less than $1.00 to about $1.50 per day based on size and how long it runs. 

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.
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