How to Find the Best Window Air Conditioner

In the US, we spend about $350 million per year cooling our homes collectively. For reference, that’s the equivalent of 6 billion pounds of greenhouse gas. And it would take almost 600 thousand cars to equal that environmental impact in a year.

What’s your little piece of this cost?

Whether you’re more concerned about saving money or saving the environment or just staying cool, we can all agree that getting the best window air conditioner is important.

Here’s how to do it. 

When a Window Air Conditioner Makes the Most Sense for You

Should you get a window AC, central AC or just grin and bear the warm days?

Before you determine how to buy the best window air conditioner, it’s important to understand what makes a window unit the best choice for you.

Through this, you can narrow down your options and select the best window air conditioner to meet your needs.

Window units make the most sense when one or more of the following are true:

  1. Saving money is high on your priority list
  2. Comfort is important to you
  3. Someone in your household has health concerns that require a more controlled household temperature, allergens or humidity
  4. You live in an area with relatively temperate summers that have bouts of hotter weather
  5. You have a relatively small house
  6. You have a larger house, but you’re content with keeping one area of the house cooler than the rest
  7. You rent so you can’t put in a central system
  8. You tend to spend most of your time in 1-3 rooms
  9. Your central air can’t seem to keep the upstairs cool

If any of these are the case, you’re the ideal candidate for a window A/C.

Be Clear on the Difference Between Affordability & Value

As we begin to look into how to buy the best window air conditioner, it’s important to make a very clear distinction between affordability and value.

Affordability means that you can afford the unit. Value means that you get your money’s worth.

For example, a small unit could cost you as little as $100.

Wow! What a deal! You exclaim.

And we say: Not so fast.

How large a room can you cool with your new best window air conditioner? 

This air conditioner may be the perfect size. Or it may leave you hot and frustrated.

If it’s the former, then you would have spent too much if you bought a larger unit because you could have cooled the room with a $100 one.

If it’s the latter, it was affordable. But it wasn’t a value. It hasn’t actually served its purpose. In fact, you may have to spend more elsewhere to compensate for this unit’s lack.

Unit’s range in price between around $100 and $1000. To get the right value, balance what you can afford with what you need. Now, that’s value.

Energy Efficiency

It goes without saying that some units are more energy efficient than others. And energy efficiency would be on most of our checklists when searching for the best window air conditioner.

A unit may cost less initially but may cost you more in electricity and filters. Or it could be the other way around.

Let’s look at how to determine the energy efficiency of a window unit.

The efficiency of an air conditioner is measured by its energy efficiency ratio (EER). This is composed of its ability to cool to its energy usage.

Ability to cool is measured in BTU (British thermal units) per hour. Energy is measured in watts.

We may have totally lost you there. But fortunately, you’ll find this info easily identifiable in the best window air conditioner descriptions. In fact, the EPA requires that manufacturers include it along with an energy star rating.

This will help you compare apples to apples to get the highest efficiency for the best price. Some units may additionally have energy-saving features that we’ll discuss next.

As a general rule, an EER of at least 12 is considered energy efficient. But also look for that Energy Star rating for an extra layer of certainty that you’re buying an eco-friendly air conditioner.

Control Options & Features

Some common options to consider when finding the best window air conditioner would be the following:

  • Programmable thermostat
  • Easy access filters
  • Digital temperature control
  • Sleep settings
  • Timers
  • Variable fan speeds

Let’s look at each of these features and why you might want to consider them when choosing the best window AC.

Programmable Thermostat

The programmable thermostat allows you to manage your unit without having to constantly do it manually.

Perhaps you typically get home from work at 6:30 PM. You can set the unit to turn on at that time every day or on certain days.

When you go to sleep, you might open windows to feel the night breeze. You don’t need the unit, so you could schedule it to go off at your usual bedtime.

These settings allow you to further reduce the cost of running the window unit.

Some units may also allow you to program specific temperatures for various times during the day when combined with a digital temperature control as we’ll discuss next.

Digital Temperature Control

If you buy a very basic unit, it will only have low and high. You won’t have much control over the temperature in your room. It’s either hot when the unit’s off. Or it’s cold when it’s on.

But more advanced units may have a digital thermometer, similar to a central unit, that allows you to choose the ideal temperature for the room. 

The unit will then measure the indoor temperature and adjust its output. Or it may even turn itself off temporarily to maintain the desired temperature.

No more leaving your AC on accidentally on a cold day, while you’re not home.

Easy Access Filters

Your best window air conditioner filters will remove allergens and other debris from the air. You can breathe more easily with this feature.

But if your air conditioner has filters that are hard to access or expensive, you may not change them as often as you should.

Before you buy, research the cost of filters and how often they must be replaced. Determine what kind of maintenance may be required. Look for a window AC that has filters that can be easily replaced.

Sleep Settings

This can be part of a programmable timer or a separate feature, so we’ll cover it separately.

Some units will have a thermostat that’s specifically designed to reduce the AC output at night to save energy.


There are various levels to the bells and whistles on the best window air conditioner. You may not want to splurge on a programmable thermostat, but you still want something to help you save energy and money.

Enter the AC timer. It’s exactly what it sounds like. You set the timer and it reminds you when to turn the unit off, like right before bed or when you leave for work.

Variable Fan Speeds

Basic units may have one fan speed. Or they may have a high and low that corresponds to room coolness.

But sometimes you want a high fan for circulation. But you really don’t want the room to be cooler. Variable fan settings allow you to adjust the fan separate from the cooling system so that you’re not using more AC than you have to.

Cooling Capacity Needed

To determine the size needed, we’ll refer back the BTUs that we discussed a little earlier.

We said that the BTU is the measure of ability to cool. But in terms of sizing a window unit cooling capacity, it’s the size of the room that it has the ability to cool.

As we discussed, if the unit is too big, you’re using more energy than you should. If it’s too small, you can’t get the room cooled to your liking. 

On top of that, if the unit is too small, then it may strain to try to live up to the expectations you’ve set for it to cool the whole room. As a result, it won’t do a very good job and its lifespan will be cut significantly.

To find the best window air conditioner for a certain room, measure the room with a tape measure. Never eyeball it. This is worth the precision. 

If you have an open floor plan, measure the whole area and buy accordingly. The unit can’t tell the difference between rooms if there are no doors or walls between them.

Now, some basic math will ensue.

  1. Multiply the width times the length of the room to get the number of square feet in the room
  2. Multiply the square feet by 20. It takes 1 BTU roughly to cool 1 square foot

There’s another step. But first, let’s walk through an example.


Your room is 20 feet long and 12 feet wide. This would be a small living room in the average 3 bedroom house. To keep it simple, we’ll assume that this room is closed off by a door from the adjoining rooms. So you’re only measuring this room.

20 X 12 = 240

You multiply 240 by 20 BTUs

240 X 20 = 4800

Looks like you need 4800 BTUs to cool this room. But there’s one more step to get a truly accurate estimate of BTUs needed.

If you live in a warm climate or the room is facing the afternoon sun, add 10% to the BTUs needed. If the room is upstairs where heat rises, you may want to add 10% for that as well.

Whenever possible, choose a spot for your newly purchased best window air conditioner in the shade to avoid the need for extra energy usage.

If you live in a cooler climate that is only slightly warm on some days or the window is shaded well by a large tree, etc., then subtract 10%.

To continue with our example, we’ve determined that the BTUs needed are 4800. But the window is well shaded. So…

4800 X .90 (90%) = 4320

You’re looking for a unit close to 4320.  The smallest units are 5000 BTU, so the best window air conditioner for you in this example is one of the smallest units.

A small unit will be around 5000 to 7000 BTUs. On average, this would cool a living room as we described or around 2 small bedrooms equalling up to 300 square feet. 

A medium unit is 8000 to 10 thousand. This would cool a room of around 450 feet.

A large unit is 10 thousand to 12500 BTU. That would cool a room up to 650 square feet which might be a small studio apartment or a living room, dining room, kitchen with an open floor plan.

Size Needed

To choose the best window air conditioner for your home, you need to evaluate the space that you have for a window air conditioner.

Consider the size of your window. What is the height and width? Your air conditioner will ideally be nearly the size of that window.

If you only need a low BTU air conditioner, then the unit will be smaller than the average window. If this is the case, then you will need to install panels around it to prevent air seepage. These panels will come with most air conditioners.

If you don’t have a window in which to place a window A/C, portable air conditioners are another option for you.

These units can sit on the floor. They suck warm air and humidity out of the room and release it through a hose that you would put out a window. They then blow cold air into the room.

Despite their small sizes, they can cool medium to large rooms similarly to a medium or large window unit. They are often quite heavy, but may have rollers so they can be moved.

Portable air conditioners can be more energy efficient than other options, if you need to cool a smaller space.

Find the Best Window Air Conditioner for Every Space

Buying the best window air conditioner is important. It’s not just about the money you spend now on the unit. It’s the cost of energy over time. It’s the comfort — or lack thereof — that you experience. It’s the ease of use.

It’s not easy and you don’t have to figure this out on your own. We’re Portable Air Cons. We test the units and provide you with our recommendations. Check out our reviews before you buy your next air conditioner.

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