7 Most Energy-Efficient Window AC Units (Under $149,32/Year Cost)

Nobody likes to pay extra for electricity (especially if you don’t have to). That’s why we have created an all-in-one overview of the absolute most energy-efficient window air conditioners on the market.

Choosing any one of them will reduce the 20-year electricity expenditure by at least $434,23 (compared to standard-efficiency units). In terms of coal burned, that’s about 3378 lbs less coal being burned in the next 20 years just because you picked an efficient window air conditioner.

Here’s the deal:

You have to get this right the first time. If you don’t buy the most efficient window air conditioner on your 1st try, you will probably have to live with higher-than-average electricity costs for the next 20 years.

To avoid having to spend $1,000 extra on electricity in the next 20 years, you should inform yourself about exactly which window air conditioners are the most efficient. Once you buy one, you can’t really replace it with a better energy-efficient window AC unit; that will again incur the next costs of the device, and you will be paying extra.

This is the exact thing we want to avoid here. That’s why we will go into:

• What energy-efficiency ratings you should be looking for when choosing the best energy-efficient window AC units.
• How to correctly size a window AC unit for the room size. Overkill AC capacity will unnecessarily boost electricity costs.
• Bring you the 7 most energy-efficient window air conditioners with absolute over-the-top EER and CEER ratings. Choosing any one of them will reduce your future 20-year window AC running costs by at least $434,23 compared to average energy-efficiency units.

We will go through the 3 key things to look for in order to maximize the energy savings. Based on these, you can find the most energy-efficient 5,000 BTU, 6,000 BTU, 8,000 BTU, 10,000 BTU, 12,000 BTU, 15,000 BTU, and 18,000 BTU window AC units. You can jump to the list of the best energy-efficient window air conditioners (with comparison and reviews) here:

Skip To List Of Best Efficient Window AC Units

Choosing a power-saving window air conditioner doesn’t start with EER and CEER energy-efficiency ratings, or even Energy Star ratings. It starts with properly sizing a window AC unit:

How To Choose The Right Size Of Window AC For Maximum Energy-Savings

You need to know exactly how many BTU cooling capacity you need. Window air conditioners range anywhere from:

• Smallest 5,000 BTU window AC units. Appropriate for spaces up to 150 sq ft.
• Biggest 18,000 BTU window AC units. Appropriate for spaces up to 1,000 sq ft.

To spend as little as possible to run a window AC, you should properly calculate the BTU cooling requirement.

Here is the reasoning behind ‘why are properly sized window ACs more energy-efficient’:

“A unit that is too big will be less effective and offer reduced air conditioner efficiency. Air conditioners remove both heat and humidity from the air. If the unit is too large, it will cool the room, before it has a chance to remove the humidity. The result will be a room that’s not very comfortable to spend time in.” (Source: Energy Star)

That means that you have to know the square footage of a room or an apartment that you want to cool down. Highly efficient window AC units will cool down anything from the smallest 150 sq ft rooms to a bigger 1,000 sq ft area.

EPA’s rule of thumb for AC sizing states that you should “use 20 BTU per sq ft”. That means that for, let’s say, a 400 sq ft room you would require about 8,000 BTU window AC. However, this is only a rule of thumb.

Energy Star, on the other hand, specifies how many BTU window AC units you need for the most energy-efficient cooling.

Here is a table of square footage to BTU directly from the Energy Star organization:

Area (Sq Ft)	Max. Efficiency Capacity (BTU)
100-150 sq ft rooms	5,000 BTU
150-250 sq ft rooms	6,000 BTU
250-350 sq ft rooms	8,000 BTU
350-450 sq ft rooms	10,000 BTU
450-55o sq ft rooms	12,000 BTU
550-700 sq ft rooms	15,000 BTU
700-1,000 sq ft rooms	18,000 BTU

These are the fairly exact square footage estimated for mot efficient window AC cooling. You can add or reduce capacity by 10% if you have a sunny or heavily shaded room, respectively.

Once you have nailed down the window AC capacity as accurately as possible, you should look at the 2 key metrics (EER and CEER ratings) used to determine exactly how energy-efficient window air conditioners are:

EER Rating (Most Efficient Window ACs Have 10+ EER Rating)

EER rating is the most well-known energy-efficiency metric for window air conditioners. EER stands for Energy-Efficiency Ratio ratio. It has been around since the 1970s and can adequately answer the following question:

“Is the window air conditioner energy-efficient or not?”

What is more, the EER rating can give you a good estimate of how energy-efficient the window air conditioner you’re looking at is. You will find the EER rating on the specification sheets of most window AC units; under the segment ‘Electricity requirements’.

Basically, EER is simple a ratio of the maximum BTU cooling output divided by the maximum power input (wattage).

Example: 12,000 BTU air conditioner has a maximum power draw of 1,200 watts. Here is how the EER rating is calculated:

EER rating = 12,000 BTU / 1,200 W = 10

What EER rating do most efficient window air conditioners have?

Here are the benchmark efficiency levels for window air conditioners:

• EER below 9 = Low-efficiency window AC units.
• EER between 9 and 10 = Average-efficiency window AC units.
• EER 10 or above = High-efficiency window AC units. 

As you will see in the comparison table below, the highest EER window air conditioners can reach a 12.0 EER rating. The overall most energy-efficient window AC unit – Midea U Inverter – tops even 12.0 EER with the incredible 15 CEER rating.

Now you’re probably wondering what is CEER rating, right? Lets’ explain that as well:

CEER Rating (New Combined EER Rating; Should Be 10+ For Efficient Window AC Units)

If you open the specs sheet of newer window AC units, you won’t find the EER rating. Instead, you will see the CEER rating.

CEER or Combined EER rating is the new energy-efficiency rating for window air conditioners. It gives a little better estimate of how energy-efficient the window AC unit is than the EER rating.

The main difference between EER and CEER is that CEER rating additionally accounts for electricity expenditure of window AC’s standby mode. According to DOE, when on standby, a transformer in the window AC unit will account for about 75% of the power draw. The total power draw is 1.4 watts, based on DOE statistical analysis, and CEER presumes 5115 hours of this standby mode.

In practice, CEER is very close to the EER rating.

Example: GE Profile PHC06LY is the most energy-efficient 6,000 BTU air conditioner currently on the market. It has a 12.2 EER rating and which is equal to an 11.5 CEER rating.

Here is the bottom line:

If you want to pick a highly energy-efficient window air conditioner, pick a unit with an above 9.5 CEER rating. The most energy-efficient window AC unit ever designed – the Midea U Inverter – has the incredible 15.0 CEER rating (thanks to an outstandingly efficient inverter compressor).

Estimated Yearly Electricity Cost (Up To $149,32/Year For Best Efficiency Units)

Basically, we’re adequately sizing and picking the highest EER and CEER ratings for a single goal:

To pay less for electricity. 

How much electricity a window air conditioner will spend is determined by:

• Cooling capacity. Higher BTU window AC units will, of course, spend more electricity.
• Energy-efficiency. Denotes by EER and CEER ratings. Higher EER and CEER rated window AC units use substantially less electricity.

With every efficient window air conditioner, you will get an EnergyGuide estimate of how much you’re looking to spend on electricity for running your window air conditioner. These calculations take into account normal use and average electricity costs.

If you look at the table below, you will see the absolute minimum electricity expenditure you can look forward to when selecting the most energy-efficient window air conditioners.

Example: A standard-efficiency 10,000 BTU window AC unit (with a 9.5 EER rating) will require about $89 worth of electricity per year to run. Midea U Inverter – the most energy-efficient window air conditioner – will require only $47 worth of electricity per year to produce the same cooling effect.

Just by choosing this incredibly efficient window AC unit, you’re effectively saving $42 per year. In 20 years – the maximum lifespan of window AC units – that results in a total of $820 saved on electricity bills. That’s the price of the new iPhone, for example.

In short, it really pays off to check those EER and CEER ratings. Not only will you pay less for electricity, but you will also help the environment because the power plants won’t need to burn additional coal, gas, etc. to cover the non-efficient window AC unit energy needs.

With all this in mind, let’s finally look at the most energy-efficient window air conditioners by BTU cooling output:

List Of Most Efficient Window Air Conditioners (By EER, And BTU)

1. Frigidaire FFRE053WAE: Most Energy-Efficient Smallest 5,000 BTU Window AC Unit.
2. GE Profile PHC06LY: Best Energy-Efficient 6,000 BTU Window AC Unit.
3. Taotronics TT-AC003: Most Efficient 8,000 BTU Window AC Unit (Quietest Window AC Unit)
4. Midea U Inverter: Most Energy-Efficient 10,000 BTU Window AC Unit (Most Efficient Overall)
5. Della 048-TL-WAC12K: Most Energy-Efficient 12,000 BTU Window AC Unit.
6. hOmeLabs B084WQ1KMT (Very Popular Choice): Most Efficient 15,000 BTU Window AC Unit.
7. Frigidaire FFRE1833U2: Most Energy-Efficient Biggest 18,000 BTU Window AC Unit.

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1. Frigidaire FFRE053WAE: Most Energy-Efficient Smallest 5,000 BTU Window AC Unit

The smallest window air conditioners are in high demand. Everybody with a small 10×10, 12×12, or 14×14 room is looking to properly cool it down with as little difficulty as possible. To reduce the cooling electricity costs the most, you should look into the Frigidaire FFRE053WAE air conditioner.

Frigidaire FFRE053WAE is the smallest window air conditioner. It can generate 5,000 BTU of cooling output with is, according to Energy Star, enough to cool down rooms up to 150 sq ft. All rooms up to 14×14 fall into this square footage.

To produce 5,000 BTU of cooling output, the 10 EER rated units would require 500 watts of electrical input. Frigidaire FFRE053WAE, on the other hand, is even more efficient. It can generate 5,000 BTU of cooling output by running on only 410 watts. That means it has a CEER rating of 12.1. In short, this is the best efficient small window air conditioner.

To run for a full season, the estimated yearly cost according to EnergyGuide is $40/year. That’s it. Standard-efficiency 5,000 BTU units require about $62/year worth of electricity; running the Frigidaire FFRE053WAE for 20 years will reduce your electricity bill by a total of $434,23.

On top of that, this unit is made by Frigidaire, a well-known and respected window air conditioner brand. It’s the most energy-efficient smallest 5,000 BTU window AC unit on the market:

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2. GE Profile PHC06LY: Best Energy-Efficient 6,000 BTU Window AC Unit

For rooms up to 250 sq ft, you will require a 6,000 BTU window AC unit. By choosing an energy-efficient one, you can save up to $500 in electricity bills alone in 20 years. The most energy-efficient 6,000 BTU unit is the new GE Profile PHC06LY.

Energy Star rated GE Profile PHC06LY is the highest EER rated window air conditioner. It has an over-the-top 12.2 EER rating; it’s about 30% more energy efficient than standard units. To produce 6,000 BTU of cooling output, it doesn’t require 600 watts; it runs on 490 watts maximum.

GE is so confident in their new GE Profile PHC06LY unit that they additionally measured the CEER rating (Combined EER rating). GE Profile PHC06LY’s CEER rating is 11.5 CEER; way above average, and makes it the most energy-efficient 250 sq ft window air conditioner.

The total yearly electricity expenditure according to the government-issued EnergyGuide label is $52. That the minimum electricity cost to cool down up to 250 sq ft space.

GE Profile PHC06LY is, all in all, one of the best window AC units. It has a low profile, leaving more space for natural light to enter the room (hence the ‘Profile’ in the name).

GE, of course, is also a reputable brand that produces reliable and highly energy-efficient window AC units. The GE Profile PHC06LY is, in short, a window air conditioner with the highest EER rating:

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3. Taotronics TT-AC003: Most Efficient 8,000 BTU Window AC Unit + Quietest Unit (Up To Only 43 dB)

Taotronics TT-AC003 is one of the few window AC units with very low (below 50 dB) noise levels. This is due to the highly energy-efficient and quiet compressor that produces remarkable specs, namely:

• Very high energy efficiency: 12.0 EER rating (Energy Star certificate, of course).
• Record low noise levels. With only 43 dB top noise levels, the Taotronics TT-AC003 is the quietest energy-efficient window air conditioner.

Taotronics TT-AC003 is a modern 8,000 BTU air conditioner with a more eco-friendly design and operation. It is powerful enough to adequately cool down spaces up to 350 sq ft.

The key point is that all that cooling power is generated via an energy-saving operation. The new Taotronics TT-AC003 compressor is to be thanked for the tremendous 12.0 EER rating. Taotronics TT-AC003 requires only 660 watts of power input to produce 8,000 BTU of cooling effect.

That puts its yearly electricity expenditure to as little as $65/year. $65 is quite a small price to pay to have a 350 sq ft room cool during the summer. On top of this, you have a very quiet window AC unit that produces the least amount of noise possible.

All in all, Taotronics TT-AC003 is not only the best 8,000 BTU energy-efficient air conditioner. It is the quietest window AC in general and thus one of the most popular choices overall:

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4. Midea U Inverter: Most Energy-Efficient 10,000 BTU Window AC Unit (Best Of The Best)

Midea U Inverter is the first next-gen window air conditioner. The double use of the inverter compressor and over-the-sill design has made this unit the most popular window air conditioner to buy in 2023.

There is clear reasoning behind this: the advanced inverter compressor allows the Midea U Inverter to hit the record-high CEER ratings. This is undoubtedly the most energy-efficient window air conditioner in 2023 (it was even certified as such in 2020 and 2021 by Energy Star).

First of all, all Midea U Inverter models (8,000 BTU, 10,000 BTU, and 12,000 BTU) have a record-high CEER rating of 15. 15, this is not a typo. That makes it at least full 35% more energy-efficient than standard models.

If you remember, the highly-efficient Soleus Air Exclusive has a yearly running cost of $70/year, and that’s for an 8,000 BTU model. Midea U Inverter 10,000 model, for comparison, has an EnergyGuide certified yearly electricity expenditure of only $47. That’s unheard of for a 10,000 BTU mode.

In short, Midea U Inverter is in a class of itself. It’s 2 classes more energy-efficient than the most efficient window air conditioners, it has the quietest operation, and it is overall the best window air conditioner in general. You can choose between 8,000 BTU, 10,000 BTU, and 12,000 BTU model; all of them at the smartest window AC picks in 2023.

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5. Della 048-TL-WAC12K: Most Energy-Efficient 12,000 BTU Window AC Unit

For a 12,000 BTU air conditioner, you will need more than 1000 watts of power input. The trick with this kind of most energy-efficient 500 sq ft window air conditioner is to go as little over 1000 W as possible. Della 048-TL-WAC12K is the best 12,000 BTU unit that can run on a maximum of 1250 W.

12,000 BTU of cooling output that Della 048-TL-WAC12K generates can cool down spaces up to 550 sq ft in total. The maximum power input of 1250 W assures the 12.0 CEER rating of this window unit.

Della 048-TL-WAC12K is also the first unit for which you’ll need more than $100 per year to run; it’s because it’s bigger, of course. According to its EnergyGuide, the Della 048-TL-WAC12K has an estimated electricity cost of $110/year. Compared to standard-efficient units, you’re saving about $40 per year or about $800 per 20-years on electricity bills alone.

All in all, bigger 12,000 BTU units can be very cost-saving as well. Even more so because they have higher overall electricity requirements; cutting that for 20-30% will reduce the electricity bills substantially. Della 048-TL-WAC12K is the best of such 12,000 BTU window AC units to buy:

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6. hOmeLabs B084WQ1KMT: Most Efficient 15,000 BTU Window AC Unit

15,000 BTU is the most powerful AC cooling capacity that doesn’t require 210/230V. hOmeLabs B084WQ1KMT still runs on 115V and can be plugged into any standard outlet. Of all the 15,000 BTU units, hOmeLabs B084WQ1KMT is the most efficient one with an 11.8 CEER rating.

hOmeLabs B084WQ1KMT can, with 15,000 BTU cooling output, be used to cool down bigger places up to 700 sq ft, according to Energy Star. Of course, to cool down such large spaces, the input wattage is sufficiently higher; the trick with the best efficiency window air conditioner is that is not all that high.

B084WQ1KMT model requires only 1270 watts to generates a substantial amount of cooling output. It has a total CEER rating of 11.8; superb for such a big 115V window air conditioner.

How much does it cost to run this energy-efficient 15,000 BTU unit?

$125/year as clearly specified in the hOmeLabs B084WQ1KMT’s EnergyGuide label. This is a 1+ ton AC unit, after all, and still, it requires a lot less electricity than the smallest central air conditioners.

Here’s the bottom line:

If you’re looking to cool down larger spaces (up to 700 sq ft), don’t want to upgrade the electric circuit to 220/240V, and would like to pay as little as possible for running cost, the hOmeLabs B084WQ1KMT is the right 15,000 BTU energy-efficient window AC unit for you:

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7. Frigidaire FFRE1833U2: Most Energy-Efficient Biggest 18,000 BTU Window AC Unit

Frigidaire FFRE1833U2 is massive. With 18,000 BTU of cooling capacity, it’s the biggest window air conditioner that still makes sense (for higher BTU, rather choose 2-zone mini-splits). It has the highest power requirements; that also means that choosing the energy-efficient 18,000 BTU unit like Frigidaire FFRE1833U2 can save you the most in electricity bills.

18,000 BTU of cooling output the Frigidaire FFRE1833U2 can generate is enough to cool down spaces up to 1,020 sq ft. That’s a small house or a big apartment. To generate all this cooling power, the Frigidaire FFRE1833U2 should, if it were a standard-efficiency unit, use at least 2,000W.

Frigidaire FFRE1833U2 is not a standard-efficiency unit, however; in fact, it’s the most powerful energy-efficient window air conditioner. It requires only 1530W power input to cool down 1,000+ sq ft spaces.

You’re looking at the minimum yearly electricity expenditure for such a big window AC unit:

Only $149,32/year according to DOE’s EnergyGuide.

Comparable standard-efficiency units will require about $208/year worth of electricity. Frigidaire FFRE1833U2 reduces this cost by as much as $58 per year, or $1,060 per 20 years.

In short, Frigidaire FFRE1833U2 is by far the most energy-efficient biggest window air conditioner that can cool down your entire home:

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When looking to save on electricity bills, be aware of BTU, EER, and CEER ratings. Check the Energy Star rating and look at the EnergyGuide label for estimated yearly electricity costs. If you have any questions regarding the efficiency of window air conditioners, you are welcome to use the comment section and we can answer them together.