Last updated: February 24, 2024.
How many watts does a window AC use? Find out below, and see the most energy efficient window air conditioner & the lowest watt window AC unit. Plus, use these 3 steps to find the most efficient unit for your needs.
- Window AC wattage ranges from 400W to 2425W typically, with 884.2W being the average;
- The lowest wattage window unit, that’s also ENERGY STAR certified, is the Frigidaire FFRE053WAE;
- Based on the actual power consumption of 1,037 different units, window ACs use 0.0874 kWh of electricity p/h, 2.097 kWh p/d, 62.91 kWh p/m, & 765.47 kWh p/y, on average;
- Window ACs account for 7% of a US household’s electricity consumption per month, on average; and
- Overall, the most energy efficient window air conditioner is the GE Profile – AHTR10AC. This unit has the highest CEER (15.7) out of all ENERGY STAR certified window units.
See the most energy efficient window air conditioners by room size, below.
Continue reading to get 3 simple steps to choose the most energy efficient window AC for your needs along with a handy Window AC Room Size Chart.
Note: actual power consumption data was sourced from energystar.gov and wattage figures were sourced from manufacturers of the most popular units.
- Window AC Wattage
- How many watts does a window AC use?
- Window air conditioner energy efficiency
- Window air conditioner BTU
- Window air conditioner EER, SEER and CEER
- Window air conditioner room size / cooling area
- How to choose the most energy efficient window air conditioner in 3 simple steps
- Energy efficient window air conditioners by room size & BTU
- Final thoughts
Window AC Wattage
The average window AC wattage is 884.2W and the most common is 660W.
Overall, window AC wattage ranges from 400W to 2425W.
This is based on a study of 58 of the most popular window air conditioners on the market.
The table below summarizes the results of the study (updated for 2024).
|Window AC wattage category
Window AC wattage is listed by manufacturers. This, in general, refers to the maximum amount of watts that the unit will use under normal operating conditions.
However, startup power surges are not included. These are typically 2-3 times the listed wattage.
Startup power surges are generally not a concern for those running their window AC units from a standard outlet. This is because electrical circuits, including breakers, cater to the temporary spike in power draw.
It’s more important for those using generators and batteries to consider window AC startup power surges.
Similarly, it’s particularly important for these users to consider the amount of watts that window air conditioners use while running, in order to avoid overloading their power system. This is not a concern for those running units from the mains.
It’s worth noting that “low wattage” does not mean “energy efficient”.
It just means that the window air conditioner draws less power to run. It doesn’t mean that the unit is as effective, per watt, at cooling. More on window AC energy efficiency below.
But for those that require a low wattage window AC, let’s take a look at some of the standout units from the study (updated in 2024).
Low wattage window AC
Low wattage window ACs have a listed wattage of 600W or less.
17.2% of the most popular units studied fall within this range.
This is actually quite a large proportion of units compared to other appliances. For example, albeit closely but not exactly related, just 4.1% of portable air conditioners fall within a low amp range.
The fact that low wattage window ACs make up such a high proportion of the most popular units indicates that there’s a higher than usual proportion of energy conscious users in this market.
This is great because these units can have a significant impact on our bills and carbon footprint. More on this below.
At 400W, the lowest wattage window AC unit is the Frigidaire FFRE053WAE.
I’ll mention too, particularly for those using generators or batteries, that reviewers on Amazon are providing some useful insights.
For example, the power draw was tested and results are reported to be: 56W – 58W with the fan running and 290W – 350W with the compressor running.
Several other reviewers have completed similar tests.
This unit seems particularly popular for those using generators and batteries to power their aircon (the manufacturer notes that the unit offers “Low Voltage Start-up”).
But it’s also a good choice for those running this unit from standard outlets given its above average Combined Energy Efficiency Ratio of 12.1 (11.4 is the average).
Again, for more details, check it out, here.
As mentioned, the manufacturer’s listed wattage is the maximum amount of watts that window aircons are expected to use.
But how many watts do window ACs actually consume? Let’s take a look at this next.
How many watts does a window AC use?
Window ACs use 35.39 watts to 329.34 watts, with 87.38 watts being the average and 57.08 watts being the most common.
This is based on the actual power consumption of 1,037 different units.
As you can see, the amount of watts that window ACs actually use is considerably lower than their listed wattage.
Window AC units consume different amounts of watts in different modes, settings and cycles.
These figures show the average amount of watts used at a single point in time. Continue reading to see how many watts these units use across various durations.
The table below summarizes the results from the study (updated for 2024), showing the average amount of watts window ACs use across various categories.
|Window AC watt usage category
These results are based on the actual power consumption of 1,037 window air conditioners and assume 750 hours per year of compressor operation under typical conditions, which is then averaged.
The data was sourced from energystar.gov.
See how this window AC data compares with portable units, check out: Window AC vs Portable AC [Efficiency, Cooling, Noise & More].
But how much electricity do window air conditioners use over longer periods of time? Let’s take a look.
How much electricity does a window AC use? (In kWh)
A window AC uses .0874 kWh of electricity per hour, 2.097 kWh per day, 62.91 kWh per month and 765.47 kWh per year, on average.
The most common amount of electricity that window ACs use is .0571 kwh hourly, 1.37 kWh daily, 41.1 kWh monthly, and 500 kWh annually.
Overall, window air conditioners use between .0354 kWh and .3293 kWh of electricity per hour, .849 kWh and 7.904 kWh per day, 25.48 kWh and 237.12 kWh per month, and 310 kWh to 2885 kWh per year.
The table below summarizes how much electricity 1,037 window ACs use across various durations.
|Window AC electricity usage category
|Electricity used per hour
|Electricity used per day
|Electricity used per month (30 days)
|Electricity used per year
As you can see, there’s a massive power consumption difference between window ACs.
And your unit’s consumption may be different again.
Related: cost to run a window air conditioner – spoiler: $0.13 per hour on average, at max draw. And $3.82 to $35.57 per month assuming typical usage.
To estimate how much electricity your window AC consumes, based on your own usage, here’s a helpful calculator…
Window AC power consumption calculator
Use this window AC power consumption calculator to estimate how much electricity your unit consumes per hour, day, week, month, and year.
Enter your window air conditioner wattage (or actual consumption, if known) and how long you use it per day.
Using your unit’s wattage, which can be found on the back of your AC, will show the maximum expected power consumption under normal operating conditions. However, using test results for the typical draw will deliver more accurate estimates, but this info is not readily available.
This calculator is pre-populated with an assumed usage of 8 hours per day, along with the average window AC wattage (not the actual consumption, which will be lower as ACs don’t operate at their listed wattage continuously).
The calculated results assume a continuous steady draw throughout operation.
Continue reading to see the most energy efficient units, by room size.
But first, let’s add some context to the power consumption.
Do window ACs use a lot of electricity?
Window ACs use a lot of electricity.
They are considered energy guzzlers.
Per day, the average electricity used (i.e. 2.097 kWh) by window ACs is equivalent to:
- How much electricity a TV uses after running for over 35 hours straight;
- The power consumption of a ceiling fan after running for nearly 4 days; and
- How much electricity a freezer uses after running for over 2 days.
To add more perspective, the US Energy Information Administration notes that US households consume an average of 893 kWh of electricity per month.
Window ACs account for 7% of a US household’s electricity consumption per month, on average.
Overall, window ACs can account for as little as 2.8% to as high as 26.5% of a household’s monthly electricity usage.
This clearly demonstrates the importance of running an energy efficient model.
So, next let’s take a look at window AC energy efficiency indicators.
Window air conditioner energy efficiency
The most energy efficient window air conditioner is the model that uses the least amount of electricity to meet your needs.
It’s not a case of one-size-fits-all.
Key considerations for window air conditioner energy efficiency are:
- Power consumption;
- BTU (cooling capacity);
- EER, SEER or CEER (efficiency ratios); and
- Room size / cooling area.
We’ve already covered the first key consideration, power consumption, above. Next, let’s jump into the remaining considerations and use the results of the study as benchmarks.
This will help you identify the most energy efficient window AC for your needs.
Window air conditioner BTU
Window air conditioner BTU (British Thermal Unit) is a measurement of cooling power – it refers to the cooling capacity of the unit. Window AC BTU (DOE) ranges from 5000 to 35000, with 11897.7 BTU being the average and 8000 BTU being the most common.
The higher the BTU, the more heat will be removed from the air, per hour.
Window air conditioner BTU figures are commonly ASHRAE or DOE ratings. These ratings are simply different test procedures for identifying cooling capacity.
ASHRAE ratings are defined by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, and DOE ratings are defined by the Department of Energy. DOE ratings are also referred to as SACC (Seasonally Adjusted Cooling Capacity) or DOE SACC.
ASHRAE BTU figures are higher than DOE BTU figures, so it’s important to only use one rating method when comparing units.
The DOE rating was used in the study. All BTU results listed in this article are DOE unless otherwise stated.
The table below summarizes window air conditioner BTU results from the study of 1,037 different units.
|Window AC BTU category
As you can see, window ACs have a wide range of cooling capacities.
Combining a unit’s cooling capacity with its power consumption is a crucial energy efficiency indicator. This is where the EER, SEER and CEER figures come into play.
Related: if you’re interested in the most energy efficient appliance with both heating and cooling functionality, check out the insights from this study of the highest SEER heat pumps.
Window air conditioner EER, SEER and CEER
Window air conditioner EER, SEER and CEER are all energy efficiency ratios that are used to measure a unit’s efficiency.
EER stands for Energy Efficiency Ratio, SEER is short for Seasonal Energy Efficiency Ratio, and CEER stands for Combined Energy Efficiency Ratio.
Each measures efficiency slightly differently:
- EER is calculated by dividing the window air conditioner’s cooling capacity (in BTU) by its average power consumption (in watts).
- SEER is calculated by dividing the cooling capacity of the window air conditioner during warmer months by its power consumption.
- CEER is calculated by dividing the cooling capacity (in BTU) by the average power consumption (in watts) during on and off modes.
The higher the result, the more efficient the model.
Due to their different methods of calculation, it’s important to compare like with like.
It’s common to leave window ACs plugged in continuously, which can lead to energy wastage, so let’s look at the CEER results.
The table below summarizes the window air conditioner CEER results from the study of 1,037 units.
|Window AC CEER category
Window air conditioner CEER ranges from 9.1 to 15.7, with 11.96 being the average and 12 being the most common.
To efficiently cool your area, you should choose the window AC with the highest CEER that’s designed to cool your room size.
Next, let’s take a look at room size.
Window air conditioner room size / cooling area
Based on 1,037 units, window air conditioners can cool rooms up to 2,700 sq. ft.
It’s important to cool a room with an appropriately powerful window air conditioner.
Underpowered units may not sufficiently cool the room and overpowered units may not run enough to remove sufficient humidity.
Both underpowered and overpowered window ACs can lead to electricity wastage.
To identify the appropriate window air conditioner for your room, first identify the square footage.
To do this, simply measure the length and width of the room and multiply them together. Then use the Window AC Room Size Chart below to estimate your required cooling capacity.
Window AC room size chart
Use the Window AC Room Size Chart below to see the cooling capacity typically required for each room size.
The room size is the maximum square footage typically recommended by manufacturers for the relevant cooling capacity, in BTU (ASHRAE).
Recommended adjustments are listed at the end of the infographic. For example, it’s recommended that you increase the cooling capacity by 10% if the room gets a lot of sun.
When you identify the cooling capacity required for your room, simply find the unit that has the highest CEER (listed further below) to ensure you choose the most energy efficient model for your needs.
Now that you know the appropriate cooling capacity required, let’s take a look at the window ACs that stand out in terms of energy efficiency.
But first, let’s summarize the points above to create some actionable steps to help you choose the most energy efficient window air conditioner.
How to choose the most energy efficient window air conditioner in 3 simple steps
Follow these 3 simple steps to find the most energy efficient window air conditioner for your needs.
1. Identify how big the area is that you need cooled
To identify the appropriate window air conditioner for your room, first identify the square footage. To do this, simply measure the length and width of the room, and then multiply them together.
For example, if your room is 20 feet long and 15 feet wide, then you have an area of 300 sq. ft. (20 ft. x 15 ft. = 300 sq. ft.)
Manufacturers of AC units tend to list the maximum recommended cooling area in sq. ft. But using this alone does not ensure you’re choosing an energy efficient model. Following the next two steps will help you do this.
2. Find the required cooling capacity for your room
Use the square footage of your room to identify the recommended cooling capacity, in BTU.
There are various methods to do this. The easiest way is to use the Window AC Room Size Chart above.
Simply find your room size in the chart and note the corresponding cooling capacity / BTU figure.
For example, a 300 sq. ft. room has a recommended cooling capacity of 7,000 BTU.
Take into account the additional considerations listed at the bottom of the chart to get a more accurate recommendation for your room.
3. Find the appropriately sized window AC with the highest CEER
CEER (Combined Energy Efficiency Ratio) is a key energy efficiency indicator. The higher the CEER, the more efficient the unit.
Other indicators do exist (e.g. EER, SEER) so it’s important to compare like with like.
Finding the window AC unit with the highest CEER, that has an appropriate cooling capacity for your room, might take some time – that’s if the work wasn’t already done for you.
See the most energy efficient window air conditioners by room size and BTU / cooling capacity below.
Energy efficient window air conditioners by room size & BTU
Based on the study of 1,037 of the most energy efficient window air conditioners, the table below lists the most energy efficient units by room size and BTU / cooling capacity.
CEER, wattage, and annual power consumption are also included for convenience, along with links to each unit for more details.
|BTU (ASHRAE) / Cooling Capacity
|Most efficient Window AC
|Link for more details
|Power consumption p/y
|150 sq. ft.
|Frigidaire – FFRE053WAE
|Check it out, here.
|Low voltage start-up, comes highly rated and conveniently maintains a preset room temperature.
|250 sq. ft.
|LG – LW6019ER
|Get details, here.
|Also highly rated and has adjustable louvers to help control air movement.
|300 to 350 sq. ft.
|7000 to 8000 BTU
|Midea – MAW08V1QWT
|See its clever design, here.
|Achieved the coveted “ENERGY STAR Most Efficient” label. Amazon’s #1 best seller.
|400 to 450 sq. ft.
|9000 to 10000 BTU
|GE Profile – AHTR10AC
|See the latest price, here.
|15.7 is the highest CEER out of 1,037 units studied.
|500 to 550 sq. ft.
|11000 to 12000 BTU
|GE Profile – AHTR12AC
|See the price, features, and more, here.
|Similar model to the unit directly above but designed to cool even larger rooms.
|600 to 650 sq. ft.
|13000 to 14000 BTU
|LG – LW1517IVSM
|Get details, here.
|Manufacturer notes that this model can actually suit rooms up to 800 sq. ft. Achieved the “ENERGY STAR Most Efficient” label.
|700 sq. ft.
|Keystone – KSTAW15CE
|See this product, here.
|Energy saver mode and auto-cooling options are available.
|1000 sq. ft.
|16000 to 18000 BTU
|LG – LW1817IVSM
|Check it out, here.
|Achieved the coveted “ENERGY STAR Most Efficient” label. Requires a 208V or 230V supply (110V supply is standard in the US).
|1200 sq. ft.
|19000 to 21000 BTU
|No real standout performer
|An example unit in this range can be seen, here.
|A CEER of 10.3 was the highest recorded in this category. Check out the model directly above as it may be of interest.
|1300 to 1400 sq. ft.
|22000 to 23000 BTU
|LG – LW2217IVSM
|See price, here.
|Achieved the coveted “ENERGY STAR Most Efficient” label. Requires a 208V or 230V supply (110V supply is standard in the US).
|1440 to 1600 sq. ft.
|24000 to 25000 BTU
|LG – LW2422IVSM
|See details, here.
|Smart home enabled and quiet operation (as low as 44dB) – requires 208V / 230V supply (110V is the US standard).
|1800 to 2000 sq. ft.
|26000 to 29000 BTU
|Friedrich – KCL28A30A
|Get details, here.
|This 230V unit is the only ENERGY STAR certified window AC in this range.
|2250 to 2700 sq. ft.
|30000 to 35000 BTU
|Friedrich – KCL36A30A and KEL36A35A
|Check them out, here and here, respectively.
|These models tie for first place (both are 230V). There are not many efficient options within this range – these are the only ENERGY STAR certified units available in this range.
The power consumption of window ACs increases, in general, in line with the cooling capacity and recommended room size.
The CEER figures, however, are more of a mixed bag.
This, among other factors, is why (when looking for the most energy efficient unit) it’s important to start with room size, then find the recommended cooling capacity, and finally identify the window AC with the highest CEER.
Other factors, such as device features, design, etc., may influence your buying decision. But if you’re purely looking to keep your electricity bills and carbon footprint down, then the models identified above will help.
They are the standout energy efficient window ACs within their size range, based on the study of 1,037 of the most energy efficient units on the market.
But which one is the overall standout performer?
Most energy efficient window air conditioner
The most energy efficient window air conditioner is the GE Profile – AHTR10AC.
This standout performer is designed to cool medium sized rooms, up to 450 sq. ft.
It has the highest CEER (15.7) out of all ENERGY STAR certified window AC units.
See its features, design, price, etc., here.
However, as window air conditioner energy efficiency is not a case of one-size-fits-all, a different model may be more suitable for your needs.
Check out the table above to see the most energy efficient window AC by room size.
CEER is the key performance indicator for window AC energy efficiency. However, it may not be the sole consideration for all.
For example, those intending to run their units off of generators or batteries may prioritize power consumption to ensure the safe operation of the unit on their power system.
So, let’s briefly take a look at the energy efficient window AC unit that uses the least amount of electricity.
Which energy efficient window AC consumes the least amount of electricity?
Based on the actual power consumption of 1,037 units studied, the window AC that consumes the least amount of electricity is the Frigidaire FFRE053WAE, which consumes 0.0354 kWh per hour, 0.849 kWh per day, and 25.48 kWh per month.
Per year, this energy efficient model consumes 310 kWh – close to 60% less than the average for window ACs.
This model, expectedly, also featured in the “Low Wattage Window AC” section above.
Some key points to note about this standout window air conditioner:
- Offers low voltage start-up;
- Most efficient window AC for rooms up to 150 sq. ft.;
- No other ENERGY STAR certified unit consumes less electricity per year;
- 5000 BTU cooling capacity; and
- 12.1 CEER.
Check it out, here.
OK, so now that we know which unit is the most efficient overall and which efficient unit consumes the least amount of electricity, let’s take a brief look at which brands offer the most energy efficient units.
Most energy efficient window AC brand – 85 brands ranked
Grouping the most energy efficient units by brand, the table below ranks 85 brands that offer the most energy efficient window ACs in order of most to least efficient.
Each brand’s certified energy efficient units are combined and the average CEER and annual power consumption figures are listed.
The table is arranged from highest to lowest CEER.
|Window AC brand
|Average Combined Energy Efficiency Ratio (CEER)
|Average power consumption per year
|Brothers Air conditioning
|Emerson Quiet Kool
As you can see, GE Profile window air conditioners are, on average, more energy efficient compared to other brands.
This comes as no surprise because, as mentioned earlier, they offer the most energy efficient unit on the market.
You may have noticed that their average annual power consumption is higher than other brands. This is because they generally cater to larger cooling areas.
It’s worth noting too that brands at the opposite end of the table do still offer some of the most efficient units on the market, albeit not as efficient on average as the other brands on the list.
This is because this table includes only ENERGY STAR certified window air conditioners – only energy efficient units achieve this certification.
So, now that we’ve covered window AC wattage, and know how much electricity they actually use, along with how to choose the most energy efficient unit for your needs and which brands offer the most efficient models, let’s take a look at some FAQs.
Below are answers to frequently asked questions identified during the window AC energy efficiency study.
Are window ac units 110V or 220V?
Window AC units are 110V or 220V.
The most popular window air conditioners are generally 110V (more commonly listed as 115V). This is because they are designed to cool standard room sizes and to be plugged into the standard 110V outlets.
The most energy efficient window ACs that cater to room sizes up to 700 sq. ft. (15000 BTU) require a 110V / 115V supply.
The more powerful units, designed to cool larger rooms (1000 sq. ft. or larger), require a 208V / 220V / 230V supply.
Ultimately window AC units can be 110V or 220V, so be sure to check the specs of the device before use to ensure safe operation.
Window AC vs Portable AC
Window air conditioners are more energy efficient and more powerful than portable air conditioners. They also offer a wider cooling capacity (BTU) range.
They are generally quieter, cheaper to buy, and more cost effective to run.
But portable ACs do have their benefits too, particularly when it comes to convenience.
These units offer easier installation and can be more easily moved into other rooms or closer to individuals.
Ultimately, portable ACs offer versatile cooling options that may suit certain users.
However, window ACs outperform portable ACs.
For a comprehensive comparison, check out: Window AC vs Portable AC [Efficiency, Cooling, Noise & More].
Which window AC is best?
To take subjectivity out of play, below are the best window ACs in terms of energy efficiency, popularity, and the best unit for off-grid power systems.
In terms of energy efficiency, the best overall is the GE Profile – AHTR10AC – this window AC has the highest CEER out of all ENERGY STAR certified window units.
It’s recommended for room sizes up to 450 sq. ft.
However, it’s important to match the cooling capacity with the room, and choose the unit with the highest CEER, as discussed above.
In terms of popularity, the best overall is the Midea – MAW08V1QWT – this is the #1 best selling unit on Amazon. There are a substantial amount of positive reviews, it comes very highly rated, and it has a very clever design.
It’s also the most energy efficient window AC for room sizes up to 350 sq. ft.
Check it out, here.
For RVs and off-grid power systems, the best window AC is the Frigidaire – FFRE053WAE.
Check out the Low Wattage and Least Amount of Electricity sections above for the reasoning or check the unit out directly, here.
Which window AC brand is best?
In terms of energy efficiency, the GE Profile brand is best followed by Drea and MRCOOL.
These are followed closely behind by Frigidaire, Insignia, LG, Danby and then Midea.
Each brand offers window air conditioners that operate at various levels of efficiency.
But overall, GE Profile window ACs offer the highest average CEER.
Can window AC units heat?
Window AC units can heat, but not all do.
Less than 20% of window AC units heat.
This is based on a study of 58 of the most popular window air conditioners on the market. More than 80% of these units do not come with heating functionality.
The window AC with the highest CEER (11.1) currently on Home Depot, that also heats, is the LG – LW1821HRSM.
Wattage is an important consideration for window ACs. However, their actual power consumption is even more important.
But when it comes to energy efficiency, CEER figures are key.
I hope that the insights into these figures, derived from the study, helps you identify the most energy efficient window AC for you.
I also hope that you found the most energy efficient window air conditioners by room size to be a useful shortcut to staying cool while keeping your bills and carbon footprint low.
If you’d like make even more considerable savings, don’t miss this 6 Quick Wins Cheat Sheet:
How much does it cost to run a portable air conditioner? Find out here. Also, get running costs of the lowest wattage & most efficient units. Plus, use this calculator to see your own specific costs.
How many amps does a portable air conditioner use? Find out here. Plus, get low amp portable AC details, see which unit has the lowest amp draw & see the amperage of the most efficient units.
Find out how loud portable AC units are and which is the quietest portable air conditioner in 2024. Plus, keep your unit’s noise level low with these 13 easy-to-implement noise reducing tips.
James, Eco Cost Savings co-founder and Editor-in-Chief, is also our experienced in-house energy management and sustainability expert, and manager of our network of sustainability consultants.
Before his journey into sustainability, James studied engineering. Additionally, he has experience in HVAC installation, and data analysis. A self-proclaimed practical environmentalist, and avid penny pincher, James established Eco Cost Savings to share his and his colleague’s expertise with the aim of helping to reduce energy bills and carbon footprints at scale.