The Most Energy Efficient Window Air Conditioners: Reviews and Buying Guide

The Most Energy Efficient Window Air Conditioners in 2021: Review & Buying Guide

Every single year more and more people are searching for the most energy efficient window air conditioners. They want to stay away from high bills, save the environment, and behave eco-friendly. And that’s the point – we all should behave responsibly.

I’m not happy if I have to admit the window air conditioners used to have a bad reputation and not many people considered them to be energy efficient. This kind of AC unit was more considered to be a cheap variant of how to stay cool however you or your family are on a budget.

But the manufacturers did great progress and pushed the window air conditioner forward to make them conserve energy and money. And the truth is it’s not only about the consumption of electric energy. The window units are strong players on the market and compete with other types of cooling machines.

Honest Review – The Most Energy Efficient Window Air Conditioners

I picked 7 most energy efficient window air conditioners conserving your money. The market is highly saturated and you can find many models providing very good options. The units on my lists met all the necessary requirements that are crucial for choosing this kind of unit from my humble point of view.

If you won’t like any of them or if none of them will be suitable for floor space of your room keep reading the second part of my article about how to choose the most energy efficient window AC unit and find out my pro tips and advice. They can give you a better overview of what to search for.

If you are searching for window air conditioners with heating you’ll find them in my article the best window air conditioners with heating. Not so many energy-efficient window AC units have heating functionality.

Friedrich Chill CP06G10B 6,000 BTU

This model from Friedrich is very well sold and I understand why. It’s very compact and suitable for rooms from 150 up to 250 sq. ft.

However, it’s sorted into a category “cheap for smaller rooms” it has completely everything you wish to have and maybe more. This unit belongs to the groups of the most energy efficient window air conditioners.

First of all, it has 12.2 EER which is really amazing. Furthermore, it’s Energy Star Certified plus it offers energy saver mode. However, it doesn’t provide any supplemental heating function or sleep mode. You can still rely on many useful features such as a programmable timer, digital thermostat, efficient dehumidification, and 6 ft. long power cord.

I personally like this model since it has very positive feedback on the internet and lots of satisfied users.

  • Coverage area up to 250 sq. ft.
  • Energy Star Certified.
  • EER 12.2.
  • Energy saver mode.
  • Estimated annual operating costs $48.
  • No WiFi compatibility.
  • No Sleep mode.
  • No supplemental heating function.

Haier ESAQ406T 6,000 BTU

This model from Haier offers a lot for a smaller starting price according to my point of view.

Let’s get started with parameters defined how much the unit is energy efficient. This appliance shows off a very high EER. Believe or not but it’s 12.2. And it’s not still enough. You can also rely on Energy Star Certification, Energy saver mode, and Sleep mode. It’s more than a decent offer.

If you’re looking for an energy-efficient window air conditioner suitable for bedroom, living room, or office I can recommend this. Why? Simply the biggest advantage is how quiet it is while operating. It produces only 43dB. You can imagine this level of noise like the sound of a library.

Many independent tests proved this level of noise and users claim the unit is a perfect pall into places where you chill or need to concentrate.

For the same reason, I appreciate the cross-flow fan for stronger smoother airflow, 24-hour programmable timer and strong dehumidification ability. I strongly recommend not to overlook the dehumidification level of a new air conditioner because very often it’s crucial. And it’s also a question if you!ll have to buy a dehumidifier in the future or not.

The last thing I have to point out is the design which is pretty nice for offices or living rooms where you meet with your guests. It’s a pretty nice piece for the interior.

  • Coverage area up to 250 sq. ft.
  • Energy Star Certified.
  • EER 12.2.
  • Energy saver mode.
  • Sleep mode.
  • Estimated annual operating costs $43.
  • No supplemental heating.

Frigidaire FFRE0833S1 8,000 BTU

This model of window air conditioner from Frigidaire is very energy efficient. It has everything from the most important aspects I would involve in my consideration if I wanted to buy one.

It’s Energy Star qualified and you can rely on the 12 EER. If you love to have consumption of electric energy under control you will appreciate the saver mode.

Everybody who struggles with allergies will love antibacterial filter and air ionizer. The perfect portion of nice-to-have functions is added to 24-hour programmable timer, 3 fan speeds, and full-function remote control.

I always positively rate the efficient dehumidification level. Because if you live in a humid area it can negatively affect your cooling machine, comfort, and home. If the window air cooling appliance is strong enough to handle the situation it’s a big plus. But keep in mind for the efficient operation, you need to run the machine at least 30 minutes to let it work properly and get rid of the humidity.

  • Coverage area up to 350 sq. ft.
  • Energy Star Certified.
  • EER 12.0.
  • Sleep mode.
  • Energy saver mode.
  • Estimated annual operating costs $60.
  • Average noise level.

LG LW8016ER 8,000 BTU

From my humble point of view, LG is a very good brand and a pretty decent guarantee of a quality purchase.

I must admit I love to rate very positively not only the fact this model belongs to the most energy efficient window air conditioners, but also the noise efficiency. Why? Simply I think not only our wallet is important. We need to have a good appliance we can rely on and it provides us a perfect comfort and doesn’t harm our health.

Recently LG did a great job and its models have a low level of noise on the operation. And this model is very quiet. It’s a great option for light sleepers.

The patented gold fin anti-corrosion coating you will appreciate not only during the summer season but also if you need to have the AC unit on a sill during cold winter months because you can’t store it in a home.

However, there is no sleep mode it’s still a nice helper in bedrooms or offices since it’s very quiet.

  • Coverage area up to 340 sq. ft.
  • Energy Star Certified.
  • EER 12.1.
  • Estimated annual operating costs $65.
  • Low noise level.
  • No sleep mode.

Frigidaire FFRE1233S1 12,000 BTU

This model from Frigidaire belongs to the category “mid rooms”. It’s a very popular appliance among those all window AC units.

I personally very like the energy efficient air conditioners that are designed to cool larger spaces such as this one suitable up to 550 sq. ft.

Of course, I don’t want to talk only about efficiency. It’s obvious this unit is efficient. Furthermore, the estimated annual costs per year are on average $90. It’s affordable for many homeowners.

The possible drawback you maybe won’t like is the noise level. On high fan speed, you can deal with 60dB. It’s an average value (similar to a louder conversation between two persons). But I usually say this is not an air conditioner for a smaller bedroom. This model is dedicated to mid-sized rooms and therefore, I think it’s still OK.

As an allergic person, I can recommend the unit regarding the antibacterial mesh filter and clean air ionizer. Also, the filter check, 8-way air direction control, and 24-hour on/off timer are very useful functions.

  • Coverage area up to 550 sq. ft.
  • Energy Star Certified.
  • EER 12.0.
  • Energy saver mode.
  • Sleep mode.
  • Estimated annual operating costs $90.
  • Average noise level.
  • No WiFi connection.

Frigidaire FGRC1244T1 12,000 BTU

This model from Frigidaire is a gem. It’s not only the energy-efficient unit it’s also a smart unit giving you lots of options on how to control it.

Smart units usually allow you to control them and change the settings on the smart devices like your cellphone or tablet. And this model belongs to them. You can easily download an app and set the temperature or turn the machine on or off remotely. There is a possibility to connect it with an Alexa device or Google Home.

One possible drawback I can see is that there is no heating function. I think it would be nice if the manufacturer thinks about that. It’s the last nice-to-have thing that I miss here.

Positively rating is for the lower noise level and sleep mode. They are very important if you desire to install the appliance into a bedroom. And if you want to put in on a sill of your office it’s a very good choice because the design is a top among the window air conditioners.

  • Coverage area up to 550 sq. ft.
  • Energy Star Certified.
  • EER 12.0.
  • WiFi connection.
  • Compatibility with the Alexa device and Google Home.
  • Estimated annual operating costs $90.
  • No supplemental heating.
  • No sleep mode.
  • No energy saver mode.

How to Find the Most Efficient Window Air Conditioner?

It’s not easy to find the most energy efficient window air conditioner on the market which is suitable for your home. The market is highly saturated and for somebody who is not able to distinguish the differences among the tons of models, it could be very complicated.

Before you start buying the right window air conditioner for you you should be familiar with some terms such as cooling capacity in BTU that helps you understand better some other terms like EER or CEER. I listed and described them below with some interesting examples for better understanding. Keep reading and find out more information about them!

Choosing the Right Cooling Capacity

However, many people overlook the aspect of choosing the right size cooling capacity for the specific room of your home, it’s very important to focus on it. Underestimating the cooling power can lead to higher consumption of energy. Or you can deal with a not efficient window air conditioning unit that won’t be able to cool the room properly. Then, all most energy efficient window air conditioners are useless if they don’t operate with the appropriate cooling capacity.

Remember the cooling capacity is represented by the British Thermal Units (BTU). If I should explain it very easily those units express how much energy you need to effectively cool the chosen floor space. So, how to find the BTU for your home?

First of all, you have to measure the floor space. For example your desire to use your window air conditioner for a living room and a kitchen. It means it’s needed to measure the floor space of the living room and add to the floor space of the kitchen. Measure a length and a width of the first room and multiply those numbers. You have the first-floor space in square footage. Do the same for the second room and add them together. Now, you obtained the final number you need to indicate the BTU you need.

150 sq. ft.5,000 BTU700 sq. ft.14,000 BTU
250 sq. ft.6,000 BTU1,000 sq. ft.18,000 BTU
300 sq. ft.7,000 BTU1,200 sq. ft.21,000 BTU
350 sq. ft.8,000 BTU1,400 sq. ft.23,000 BTU
400 sq. ft.9,000 BTU1,600 sq. ft.25,000 BTU
450 sq. ft.10,000 BTU1,900 sq. ft.28,000 BTU
550 sq. ft.12,000 BTU2,700 sq. ft.36,000 BTU

Keep in mind, it’s not wise to rely only on the cooling capacity in BTU defined by the floor space. You always have to involve other aspects to indicate the proper number for your home. Here are some tips on how to do it:

  • If you want to cool your kitchen or space adjoined to a kitchen it’s better to increase the cooling power by 4,000BTU. When you cook the heat is spreading and your AC unit has to work harder.
  • For very well shaded rooms (you have outdoor wooden window shutters, there is a tree in front of the window) it’s possible to reduce the cooling capacity by 10-15 percent.
  • If your room is exposed to the sun all day you should consider increasing the capacity by 15-20 percent.
  • Since every human body radiates heat, you have to add from 600 up to 800 for every person living in the apartment.

Also, it’s very important to involve the effect of the climate you live in. If you live in a hotter and humid area you will need a more powerful window air conditioner compared to other locations.

What Is Energy Efficiency Ratio (EER)?

If you are looking for the most energy-efficient window air conditioner you should definitely follow the Energy Efficiency Ratio (EER) label. You have never heard about that? Or you have but not sure what it means? Let me describe it very easily.

Every AC unit has an energy efficiency rating. And this rating represents how many BTU’s per hour are used for each watt of power it draws.

How is the EER calculated by manufacturers? Let me explain it on an example: Let’s say you want to buy an air conditioning unit having cooling capacity 10,000BTU and consuming 1,200Watts. The calculating formula is (10,000BTU / 1,200Watts) = 8.3 EER.

What is the best EER? In general, the most energy-efficient air conditioners have EER equal or above the number 12. If you’re desperately looking at the energy-saving unit try to find a machine with an EER higher than 12.

Is the higher EER rating worthy of extra cost? I can’t say clearly yes or no. Let’s observe another good example. You’d like to choose between two window air conditioners. The first AC unit consumes 1,200Watts and has 8.3EER. The second appliance consumes 1,000Watts and has 10EER. The second unit has a higher EER and it’s $100 more expensive. We can say if it’s worthy to buy the unit with a higher price only if we calculate the payback period for it.

For the calculation formula, we need to know:

  • How many hours per year you’re planning to operate the unit.
  • Rate of a kilowatt-hour (kWh) is in your area (given by the electric company).

Let’s say the cost of a kilowatt-hour is $0.10 and the difference between those two units is 200Watts. Then, the formula is:

5 mo. x 30 days/mo. x 8 hr/day = 1200 hours 
[(1200 hrs x 200 Watts) / (1000 Watts/kW)] x $0.10/kWh = $24.00

As I said at the beginning, the price difference between those units is $100. And our solution is $24. It means we need almost four years to break even.

I significantly recommend using the formula above if you’re choosing between some cooling machines and you’re not sure which one is the most energy-efficient window air conditioner for you.

I know many people are maybe wondering why window AC units don’t have Seasonal Energy Efficiency Ratio (SEER). The reason is very simple. The SEER is used only for central air conditioners. If you’re buying a window unit you need to follow this ratio.

What Is Combined Energy Efficiency Ratio (CEER)?

Another term is the Combined Energy Efficiency Ratio (CEER). This rating represents a combine energy consumption. It means the rating combines the consumption of normal operating together with stand by mode.

Just like the EER, this rating is a part of the Energy Guide Label. This label is visibly attached to every box with a window air conditioner.

Energy Star Certified Products

The Energy Star Certification is another energy efficiency rating visibly attached to the Energy Guide Label. This certification is a government-backed symbol giving you a guarantee that you’re buying a truly efficient product you can rely on. This symbol helps to conserve energy and money. If you’re in a process of looking for a new AC unit I can only recommend finding this symbol on a box you want to purchase.

How Can Smart AC Units Help with Saving Energy and Money?

You have maybe heard about smart window air conditioners but you’re not sure what it means. In general, the smart window units are connected to the home network by using WiFi.

Once they’re connected to the Internet you can download an app for your smart device like a phone or tablet. It allows you to control the cooling machine remotely. It’s possible to turn the AC unit on or off, set the temperature and humidity level while you’re still sitting at work. Check out my article about smart window air conditioners.

Does it conserve your money? Definitely! And it also gives you freedom. Many of the apps allow you to control the consumption of energy and see your monthly costs. Furthermore, some models also offer compatibility with Alexa devices and Google Assistant to connect all of your smart devices and have a smart, eco-friendly, and energy-saving home.

If you want to get extra peace of mind or simply love to control your appliances I significantly recommend the smart window air conditioner as the best choice.

Saving Modes

Many of the window air conditioners offer helpful modes that have one in common. They should improve the quality of your life and your comfort. The saving mode is a little bit different because it should help you to reduce your energy bills.

If you don’t use the saving mode on your window air conditioner, the exhaust fan is turned on and off by the order of the compressor. And the circulation fan runs at the set speed.

What happens when we use the energy-saving mode? First of all, it helps to reduce energy consumption a lot. How, both the exhaust and circulation fans are automatically turned off when the compressor is turned off. When the temperature increases and it’s really needed to start to cool again, both fans are run again.

Keep in mind the energy-saving modes aren’t available for cheap window AC unit having rotary dial controls.

Sleeping Modes

If you are familiar with a sleeping mode you know it’s a very comfortable function. If not, let me explain to you how it works and how it helps you reduce energy consumption.

Since our bodies don’t need to be cooled so much during the phase of sleep, the sleep mode works on the principle of increasing the temperature throughout the night. Every single hour is the temperature increased to one degree until you wake up. You’re woken up by in a little bit uncomfortably temperature which actually much more natural for human bodies. The window AC machine is powered lower when operating the sleep mode and therefore it conserves money and energy.

Many of the window air conditioners on the market offer this function except the cheapest units. I can recommend buying a cooling machine with the sleeping mode. You will be amazed at how much it helps you not only to save money but also to improve your sleep.

Additional Tips on How To Reduce Reduce Energy Costs

Even the best functions and features aren’t a guarantee of reducing your energy bills according to your wishes. Therefore, sometimes it is better to focus also on other options on how to protect your home. I summarized some of them and I believe it could help a lot:

  • Use at home indoor sun-blocking window curtains or outdoor wooden window shutters to protect your home against sun rays.
  • Buy a ceiling fan and use it. It improves the circulation of air in a room.
  • Try to stay away from using grills, ovens, and similar appliances on hot days.
  • If you own any portable fan, you can use it in a combination with a bowl of ice. It helps to spread the cool air faster and it’s cheap.


The window cooling machines are considered to be affordable, easy to use and easy to install. They have lots of fans. The manufacturer did great progress and has started to upgrade these types of air conditioners to keep up with the modern lifestyle. But to be honest for most of us, one of the biggest aspects is still the price and overall costs. Therefore, we instinctively look for the most energy-efficient window air conditioners. I think it’s completely normal.

I really recommend using my formula (in this article) to calculate the monthly costs for operating the unit. Then, it’s easy to consider if the unit is worthy or not. You can easily find out if your energy bill will or won’t increase and if it’s affordable for you to operate the unit.

Read this for more info about the best window air conditioners. If you’re still not sure about the right window AC unit for you, my unbiased review of the best and efficient cooling machine gives you a better overview.

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