Finding the right window AC unit for your home
The best window air conditioner is one that provides the right level of comfort for a given room size, at an affordable total cost (sticker price plus operation) while giving you quiet and durable operation. How much should you pay for a good window air conditioner? Is the Home Depot air conditioner you see on sale for $99 a good investment, or will you regret it later when your electric bill skyrockets or the grinding compressor keeps you up at night?
In this article I will cover the basics of the best window air conditioner and let you know not only what the right type of air conditioner may be for your application, but how you can get more cooling, for less expense, even with the air conditioner you already have.
You can skip ahead to any of these sections:
- Tips for cutting your cooling costs
- Choosing the right size of window air conditioner
- Energy efficiency standards for window air conditioners
- Energy efficiency vs. sticker price – how to choose
- Other selection criteria for window air conditioners
- What’s in a name: brands to choose, brands to avoid
If you’re serious about staying cool in hot weather without spending a fortune, you should first look at ways to reduce the amount of work your window air conditioner needs to do. After all, the best window air condiitioner is actually the one that doesn’t have to do much work because you’ve found ways to stay cool without air conditioning.
There are really four main ways you can cut your cooling demands while minimizing your dependence on air conditioners:
- Reduce the heat load on the room – stop it from getting hot!
- Take advantage of evaporative cooling
- Take advantage of cool night temperatures.
- Increase your tolerance to warmer temperatures
Each of these on its own can have an impact on how much electricity you use on air conditioning. If you take care of all four you can get by with a lot less air conditioning, and on a much smaller electricity budget, than if you justlook for the most energy efficient air conditioner and pay no attention to reducing your demand.
Reducing heat load: If you can find ways to keep a room from getting hot in the first place, you won’t have to cool it with an air conditioner. Obviously you can’t stop all heat from getting into the room, but there are ways to reduce heat burden. An obvious first step is to consider energy saving window coverings such as curtains or blinds, that cut out sunlight, and provide an additional layer of insulation between your window glass and the room. Leaving the curtains or blinds open on a hot sunny day significantly increases the heat load on the room.
Another thing to try is energy efficient window film, a semirigid plastic film you apply to your windows to cut out infrared spectrum light (light radiating into your room as heat) while letting most natural sunlight into your room.
If the room you are cooling is below an attic, it can sometimes feel like the room is an oven. Attics tend to get very hot on sunny summer days – up to 150F in the afternoon – because the sunlight shines on dark shingles, and the heat from the shingles radiates down into the attic space where it becomes trapped. There may be some easy things you can do to reduce the temperature in your attic, which will also cut heat flow into rooms below the attic. Many older homes were built with inadequate venting of their attic spaces. You or a qualified roofing contractor can easily install additional roof vents near the ridge and in the soffits, so that natural convection cycles pull cooler air up from below and flush the hot air out above. This reduces the amount of heat radiating down through the attic into the room. Another approach is to install Reflectix brand insulation along the attic rafters – an easy job if you’re handy with a stapler and a pair of scissors. This insulation reflects radiant heat back outside before it turns into convective heat inside the attic, and can considerably lower the heat burden on rooms below the attic.
A whole house exhaust fan is one other thing you might consider if you own your own home. These fans install in the ceiling of an upstairs room; they have a high powered fan that pulls air from the ceiling of the living space into the attic. Use a whole house exhaust fan when the temperature is warmer inside than out. For example, when you get home from work, if your air conditioners have been running on low (or turned off), and the temperature has begun to drop outside, you can use the whole house fan to pull warm air from outside into the house, while pushing hot air from the house into the attic, which in turn expells the very hot air into the attic to the out of doors. This provides moderate cooling to your living space, but more importantly, flushes out all that very hot air from the attic so it doesn’t radiate down into your rooms.
Take advantage of evaporative cooling. As you may have learned in a high school physics class, evaporation is a cooling process. When a liquid evaporates into a vapor, energy in the form of heat is taken out of the liquid in order to make the liquid change state. That’s why you feel cold when you shut off the shower, before you’ve had a chance to dry yourself.
The easiest way to take advantage of evaporative cooling is to use a fan in place of an air conditioner, wherever possible. Human beings evolved on the hot savannah of Africa, and we didn’t have the best window air conditioner back then! Instead, we sweated, and as wind or breezes blew by, the sweat evaporated, which cooled our bodies. Surprisingly, this evolutionary adaptation still works today! And while a bedroom may not be as breezy as Maropeng (the “cradle of humankind” in South Africa) was 50,000 years ago, adding a table fan or ceiling fan to a room will produce just as good a breeze, and help keep you nice and cool. I’ve spent many a scorching night in tropical Costa Rica, where I lived for a year, with a ceiling fan pushing hot air down on my bed, and even though the temperature was 85F in the bedroom, I was cool!
Take advantage of cool nigh temperatures. Temperature variations between the daily peak (typically around 3-4pm) and the daily low (typically around 4-6am) can be as much as 30F on a hot summer day. That cool pre-dawn air is just sitting there waiting for us to take advantage of it, yet many people run their central air conditioners through the night, drawing heat out of the house in a fairly inefficient refrigeration cycle. If they just drew the cool air into the house with a window fan, they could lower the indoor temperature more quickly with far less energy use.
We use window fans instead of window air conditioners in our Toronto house. They are installed in the three bedrooms and are turned off during the day, and once it’s dark out we turn them on in exhaust mode to suck hot air out of the house and draw cooler air in through other windows that we leave open. I usually wake up in the middle of the night once or twice, and the first time I do I flick their switches from exhaust mode to intake mode (which draws the cool outdoor air inside). By the time we get up in the morning, we’re usually buried under comforters to stay warm! Once the sun is over the trees we shut all our windows and blinds and turn off the fans. This technique brings enough cool air into the house that even on sweltering hot days we stay cool indoors with no air conditioning.
Get used to being hot! The American way of life may not be negotiable, but it sure is expensive to keep the indoor temperature always at a perfect 75F in summer, even when it’s 95F or 105F outside. The fact is that the more air conditioning we use, the more dependent we become on the air temperature being within a very narrow range. I used to be extremely intolerant to heat – anything over about 85F made me very uncomfortable. But after my year in Costa Rica, where temperatures in the dry season were in the high 90’s every day, my tolerance for extreme heat improved a fair bit. If you can train yourself to tolerate even a 1 or 2 degree increase in the temperature you set your air conditioner at, you will save some energy, and if you can bump it up 3-5 degrees beyond absolute comfort, you’ll save even more.
Window air conditioners are rated by their cooling capacity in British Thermal Units or BTUs. A 5,000 BTU window air conditioner can withdraw 5,000 BTUs of heat out of a room, which is about the same amount of heat going out of a room as you would be adding to a room with a 1500 wat space heater or a 1500 watt blow dryer. Typical BTU ratings of window air conditioners are 5,000 for the smallest of rooms, 6,000 to 8,000 for somewhat larger rooms, and 10,000 or more for the largest rooms. There are even units rated at up to 28,000 BTU but I would not advise buying a window air conditioner with this high a BTU cooling capacity, because (A) such units are extremely big and heavy and challenging to install, and (B) that much cool air coming in one window may lead to very cold air near that window and suboptimal cooling further from the unit.
It’s important to choose the right size window air conditioner if you want it to perform well. A 5,000 BTU air conditioner is suitable for a room of 100 to 150 square feet (up to about 12 x 12 feet square). A general rule of thumb to follow is to multiply the square footage of the room by 15, and add 3,300, to obtain a suitable BTU rating for cooling that area.
You might be tempted to buy a larger room air conditioner to get better cooling (or a higher efficiency rating), or to buy a smaller room air conditioner to save energy, but the best window air conditioner is the one that is correctly sized – just the way Goldilocks would like it. An oversized window air conditioner will short-cycle, which means it will rapidly cool the small room to the point where the compressor shuts off within a couple of minutes of starting up. This short cycling increases wear and tear on the compressor and also makes the unit seem noisier (it’s not the continuous noise that bothers most people, but the change from silence to noise or from low to higher volume as the compressor shuts of or turns back on). An undersized window air conditioner, on the other hand, will run almost continuously, and may not cool the room adequately, or may burn out faster because it is working so hard.
There is not really that much different between the least energy efficient window air conditioner available from major retailers today, and the best window air conditioner in terms of efficiency. The US Department of Energy sets minimal efficiency standards for all window air conditioners. These standards are expressed as an Energy Efficiency Ratio or EER, which refers to the ratio between BTU cooling capacity and watts of energy use. Typical EERs for minimally efficient 5,000 BTU air conditioners are in the9.7 range – which means it takes roughly 515 watts of power to operate a 5,000 BTU unit rated at 9.7 EER at full blast (5,000 / 9.7 = 515).
The best window air conditioner should at a minimum be ENERGY STAR qualifying, which means it needs to be at least 10% higher than the standard. And in some BTU categories, there is very little in the way of window air conditioners that score more than a single percentage point higher than this 10% requirement. For example, almost every ENERGY STAR window air conditioner I looked at in the 5,000 to 5,999 BTU range had an EER of 10.7, or exactly 10% above the minimally efficient requirement, so just barely ENERGY STAR compliant. Only one model scored higher, at EER 11.0, or just 13% above the standard.
Naturally, the higher the EER of your window air conditioner, the less electricity it takes to achieve a given amount of cooling. But there seem to be basically two choices for consumers: buy the minimally efficient model (e.g. SEER 9.7 for 5,000 BTU units), or buy the minimally efficient ENERGY STAR window air conditioner (e.g. SEER 10.7 for 5,000 BTU units). Manufacturers seem to have settled on mediocrity, and ENERGY STAR mediocrity: producing the lowest efficiency units required by each of the base standard and ENERGY STAR add-on. Why? Because the know most consumers won’t bother to think through the total cost of ownership of a window air conditioner, and will focus almost exclusively on the sticker price. We pay our electric bills every month or so. The extra five or ten dollars of electricity on our monthly bill that might arise from buying the cheap, inefficient unit doesn’t hurt that much. But if we use that window air conditioner four months a year for ten years, we’re paying an extra $200 to $400 in electricity costs over the ten years – more than enough to have covered the modestly higher price of the most efficient units.
You might think from the above that the most efficient unit will cost the least over the unit’s lifetime. Conversely, if you live in an area where electricity prices are quite low, you might think buying the big box store $99 special that is at the bottom end of the efficiency scale is the most affordable approach. Neither is necessarily true.
For starters, I would caution you to stay away from the big box store $99 special – that Home Depot air conditioner you see stacked six feet high on skids as you enter the store in May or June – not just because it is likely to be the least efficient in its category of anything you can buy, but also because the quality of these cheap units is highly questionable. Let’s face it, if a $99 air conditioner dies after two years, how likely are you to go back to Home Depot and demand restitution?
On the other hand, it may not make sense for you to spend top dollar on the unit that is 20% more efficient than the minimum standard. For example, which of these two units would be the most cost effective:
- The Friedrich SS08M10 7900 BTU Window Air Conditioner – with an EER of 11.7, 21% higher than the minimum requirement, for $878
- The Friedrich CP08F10 7800 BTU Window Air Conditioner – with an EER of 10.8, only 11% higher than the minimum requirement, for $275
You’re spending an extra $603 for the more efficient unit, and you’re getting an extra 10% efficiency. Let’s assume you pay $0.10 per kilowatt hour of electricity, and the unit runs continuously 6 hours a day for 4 months:
- 6 hours/day X 4 months = 720 hours a year
- EER 11.7, 7900 BTU = 675 watts x 720 hours = 486 kwh (adjusted: 480 kwh)
- EER 10.8, 7800 BTU = 722 watts x 720 hours = 520 kwh
- Kwh per year improvement from more efficient model: 33 kwh
- Savings per year @ $0.10 per kwh: $3.30
- Payback period for the extra $603: 177 years!
(Note the ‘adjusted’ figure for the higher EER unit – this is because the more efficient unit has a slightly higher cooling capacity. I added a correction factor so that the adjusted kwh of each unit represents the amount of energy each unit would consume to provide 7800 BTU of cooling power over the 720 hours.)
As you can see, it doesn’t really make sense to spend an extra $603 on the more efficient unit, to save $3.40 a year. Of course, if you live in Hawaii, where you’re likely to need 12 months of cooling for 12 hours a day, and you pay around $0.28 per kwh, it starts to become a bit more reasonable:
- 12 hours/day X 365 days = 4,380 hours a year
- EER 11.7, 7900 BTU = 722 watts x 4,380 hours = 3,162 kwh (adjusted: 3,122 kwh)
- EER 10.8, 7800 BTU = 675 watts x 4,380 hours = 2,957 kwh
- Kwh per year improvement from more efficient model: 165 kwh
- Savings per year @ $0.28 per kwh: $46.20
- Payback period for the extra $603: 13 years
But even so, it’s hard to justify that much more cash up front, if it will take 13 years for the more efficient unit to pay for itself.
I feel a little sheepish as the owner of an energy efficiency website, suggesting to you that buying the most energy efficient unit doesn’t necessarily make economic sense. But that’s the honest truth. From an environmental perspective – if that’s your main motive for saving energy – then of course you should buy the best window air conditioner in terms of efficiency. Your purchase will not only benefit the environment, it will reward manufacturers who are focused on making the most efficient air conditioners possible. But if you just want to keep the total cost of ownership down, then the best window air conditioner is not always the most efficient one.
You don’t just want to look at cooling capacity (in BTU per hour) and the EER of a unit. You should look for other critieria such as noise levels, ease of installation, suitability for your particular type of window, whether the unit has easy to use controls, together with a remote control (or is only controlled by remote). Let’s cover some of these in more detail:
Noise level: A quiet air conditioner is generally preferable to a noisy one, but for most people it’s not the level of noise the unit makes, but how frequently that noise changes, that makes an air conditioner seem more or less noisy than its peers.
A window air conditioner that short cycles – turns on and off very frequently – can be extremely annoying. So right off the bat you need to be sure you don’t oversize your unit. Sticking a 10,000 BTU unit in a window for a small bedroom is going to make it pretty hard for you to sleep. For one thing the unit will send strong, short bursts of cold air into the room, meaning you’ll have to keep adjusting the bedding to stay warm or cool as the case may be. But you’ll also have to listen to the compressor kicking in every five minutes, then shutting off again.
Another factor affecting noise level is fan control. Some units have a thermostatic control on the fan, to shut the fan off when the room temperature drops below a threshold. This can be useful when it gets cool at night and the compressor shuts off because the room is already cooler than the desired temperature setting: you don’t want to keep pumping in cool outdoor air if you’re already cold enough! But many of today’s window air conditioners have overly sensitive fan thermostats, with the result that the fan may go on and off frequently at times when the compressor itself has stopped.
Ease of installation: The key here is to go with a brand with a good reputation for quality, and to get help if you are installing one of the larger, higher BTU units which can be quite unwieldy. Why does the brand matter? Because many of the cheaper brands cut corners in manufacturing, assembly, or packaging, and many of the cheaper units may work just fine out of the box – or they may not. There are numerous reports, among knock off and generic brands of window air conditioners, of screws that don’t fit the intended holes, product specifications that have the wrong window opening dimensions, missing parts required for installation, or other problems that usually send you running off to the local hardware store to buy extra parts to make the installation work. See the section on brands below for my recommendation on the best window air conditioner to buy for your needs.
Window type: Most of the best window air conditioner models are built for sash or slider windows. There are very few that work with sash windows, and for this article I’m assuming you are looking for a window air conditioner for your sash window. You need to measure the opening when your window is fully open, and ensure you buy a window air conditioner that is spec’d smaller than that opening. You also need to be sure the side louvers that fill the gap on either side of the unit extend wide enough to close off the opening (either that or you’ll be cutting out bits of plywood to fill in the gap).
If you can’t find a window air conditioner to fit your window, or if you don’t want to give up a huge amount of window space to an air conditioner, one possibility to consider is a portable air conditioner, which looks more like a dehumidifer than an air conditioner, rolls about on wheels, and has a small hose that sticks out the window to expell heat and humidity.
Easy to use controls are another important feature to look for, and I strongly recommend against choosing a unit that only has a remote control, no panel control. Units with only a remote control are designed that way primarily as a cost savings to the manufacturer. All it takes is for you to lose the remote control, and you’re out an air conditioner (at least until a replacement remote arrives).
A digital thermostat display is better than just a “cooler / warmer” dial. But remember that a digital thermostat doesn’t guarantee that the temperature you set the thermostat to will be the temperature the air conditioner cools the room to. Some digitally controlled window air conditioners are truly accurate; others are not, but have an adjustment dial you can use to calibrate the thermostat to the actual room temperature, so accuracy is achievable; and still others provide no way to calibrate the thermostat, so 74F on the thermostat could mean 70F or 80F in real life.
Dehumidify mode is another helpful feature available on a small percentage of the best window air conditioner models. In dehumidify mode, your air conditioner compressor runs just enough to pull moisture out of the room, but it does not really cool the room. This can be useful if you live in a humid climate and want to keep the room dry in spring or fall.
Some window air conditioners even come with a heating feature, that runs the refrigerant loop in reverse, drawing heat from the outside air into the room. This is generally more efficient than running an electric heater, provided the outdoor temperature is above about 40F.
There are dozens of brands of window air conditioners, but the best window air conditioner units are made by just two or three major manufacturers. Let’s dig into the mysteries of branding first and then I’ll tell you who to choose and who to avoid.
What’s in a name? Some manufacturers have spent decades building up a solid reputation for quality, and wouldn’t dream of packaging someone else’s junk and branding it with their company name. Other companies, meanwhile, are not manufacturers at all, they only package products made by others, slapping their brand name on. But the fact that the product was made by the company whose brand appears on it doesn’t guarantee quality, any more than a brand that has no relationship to the manufacturer necessarily implies a shoddy product.
Consider these two well known and respected brands: Kenmore and Maytag. Kenmore is the main brand sold by Sears. Sears doesn’t really manufacture anything. But they put their brand on many household products – products they have presumably vetted, will stand behind if there are quality or maintenance problems, and will replace or refund the purchase price of if you complain loud enough about a service problem.
Maytag is another brand considered very reliable – just think of the bored Maytag service man. A Maytag washing machine is assumed to be very reliable (although these days, I wouldn’t be 100% sure the Maytag washing machine is made by Maytag, at least it is sold by them and they will defend their brand’s reputation by providing good service if something goes wrong).
But when it comes to conditioning, these two brands have vastly different results. As you might expect, Kenmore sells some of the best window air conditioner models,in terms of both quality and efficiency. But the Maytag window air conditioner is not only a piece of junk that should never have been made – it has nothing to do with Maytag! and is probably the best window air conditioner to avoid! Not only will Maytag not stand behind this product, but they aren’t the ones selling it or profiting (at least directly) from its sale. Instead, Maytag sold the rights to the Maytag brand, on window air conditioners, to a company called Fedders, that was once a leader in the mass production of quality window air conditioners. Fedders fell on hard times in the early 21st century and seems to have bought the rights to the Maytag brand to try to boost sales, but they didn’t deliver a quality product, and many customers were left confused and upset when their poorly built units failed and they tried to get service from Maytag, who wanted nothing to do with these Fedder units.
There are plenty of other brands that don’t really manufacture window air conditioners, but merely repackage other companies’ products. For example, one air conditioner model, #MWF08CR, is manufactured by Midea, but carries brand names including Midea, Westpoint, Degodi and Polar Wind, while another Midea model is sold under the brands Arctic King, Westpoint, Beaumark and Uberhaus. What does this mean? It means that for any of these brands (other than Midea itself) you really have no idea what you are buying. It’s almost certainly not made by the company whose brand it carries, since these are only brand names, not the names of manufacturers. And it means you have no idea who really did manufacture it. For example, Beaumark is a Canadian brand used by the Hudsons Bay Company and related retail companies; its products could come from any of hundreds of manufacturers.
What brands should you consider when looking for the best window air conditioner? I would recommend Friedrich for any of the smaller units – up to about 8,000 BTU. They score well in consumer reviews, they offer a wide selection of features, they make all their own units, and they offer some of the more energy efficient units. Kenmore stands behind everything they sell (although as I mentioned, they don’t actually make anything!) and they seem to select the air conditioners they brand based partly on quality. And Haier has a few good products.
For larger units, LG seems to be doing a very good job in the 10,000+ BTU range, while Friedrich also does well, and Sharp is a strong contender.
I have sprinkled some of my top picks for the best window air conditioner throughout this article. As I suggested earlier, I am able to survive the torrid Toronto summers without air conditioning, so I can’t claim direct experience with any of these models. Instead, my choices are based onthe energy efficiency of each unit, the quality of the brand, reviews from customers who have bought and used the products, and reasonable price. I am confident that if you buy one of these you will be getting the best window air conditioner for your money – both the money you pay up front, and the money you pay through the unit’s life as it keeps you comfortably cool.