Window Air Conditioner Basics: All Questions Answered

Window Air Conditioner Basics: All Questions Answered

A window air conditioner, or a window A/C, is the device that is designed to cool a single room and is very popular during the hot months of the year.

The room air conditioner can be a great option for your apartment or house in case you consider that a central air conditioning system is not useful enough.

Moreover, it is also an easy-to-install option if you want to cool one room rather than the whole house.

The device is the most basic form of an air conditioning system and is normally mounted on the window or a wall. The unit is containing all the components necessary for conditioning in a single case.

Window air conditioner features a double shaft fan motor with fans on the each side of the motor. One fan is located at the evaporator side and the other is on the condenser side.

Why Do People Use Window Air Conditioners?

People use the window air conditioners because these appliances come as a prominent relief in the summer. Moreover, the window air conditioners are:

  • Affordable: Some of the small A/C models can cost as cheap as $100. However, the bigger the size of the conditioner and the bigger capacity it has – the more money it will cost you. Nevertheless. Air conditioners are a great alternative to the central air conditioning.
  • Practical: A lot of modern window air conditioners feature myriad digital controls in comparison to the earlier primitive models. Some of the new-generation A/Cs have energy-saving properties, thus help you to cut down on these utility bills.
  • Easy to install: A lot of the window conditioners are very easy to install, as they come with very detailed installation kits.

How Do Window Air Conditioners Work?

Window air conditioners are installed in the open window. They work on the principle of the refrigerator and are pulling the hot air from inside the room while returning the cooled air back into the room. In order to understand how the window A/C is working, we need to understand what it is made of.

AC insides

The insides of the window A/C include:

  • Fan blower – is a centrifugal evaporator blower that is designed to discharge the air in the room
  • Cooling coil – the coil has an air filter on it. This detail is making the heat exchange happen
  • Capillary tube – this component is used as an expansion device.
  • Operation panel – this is one of the key parts of the A/C. The panel is created to control the temperature and the speed of the blowing fan and it uses a special thermostat to monitor the temperature.
  • Filter drier – this detail is used to remove the excess moisture from the refrigerant
  • Drain pan – the pan is used to collect water that condensate from the cooling coil. The water is then discharged to the outdoor.

The outdoor details of the window air conditioner include:

  • Compressor – the detail is used to compress the refrigerant.
  • Condenser soil – this component is designed to reject the heat from refrigeration to the outdoor
  • Propeller fan – the fan is used to aid move the air over the condensing coil
  • Fan motor – the motor has a double shaft. That’s the place where the indoor blower and outdoor propeller fan are connected.

The air inside air is cooled as a fan is blowing it over the evaporator. On the outside, the heat that is drawn from the interior is discharged into the environment. Moreover, the window air conditioners are able to extract moisture from the air with the help of its refrigeration properties. Let’s look into the details of how the air conditioner works.

  • The temperature of the room is reaching the set point of the thermostat. This is automatically turning on the blower of the window air conditioner. The room air is then pulled through the air inlet grille and the A/C filter that is created to eliminate various particles and dust from the air.
  • The refrigerant is pushed through tubing in the unit, which is causing the refrigeration process. The refrigerant is then taking on and giving off the heat as it fluctuates in temperature. When the refrigerant begins to circulate through the cooling coil, it is very cold. Afterward, the blower is pumping the warm air across the coil, and the refrigerant is absorbing heat that vaporizes eventually.
  • The vapor is then directed to the compressor that puts pressure on it and pushed it through the condenser coil. Here, the vapor is giving off the heat that is discharged outdoors.
  • ​The refrigerant shifts through the capillary tube that is converting it to a low-pressure liquid again that returns to the evaporator coil.
  • This cycle is repetitive. The blower is pumping air through the cold coil to cool the air and then blows it back into the room.

One of the main things to learn about the A/C prior to buying the air conditioner is the BTU and EER values.

What Is BTU And EER?

A BTU stands for British thermal unit, which is the value of the air conditioner’s capacity. More specifically, the BT is the amount of heat needed to raise the temperature 1 pound (0.45 kilograms) of water one degree Fahrenheit (0.56 degrees Celsius). One BTU is equal to 1,055 joules.

BTU per Square cooling

Usual window air conditioner has a 10,000 BTU rating. For instance, in case you have a typical house of 2,000-square-foot area, you might need a 60,000-Btu air conditioning system. Note, that this is for the whole house and these are just estimates.

In order to accurately size an air conditioner for your room, you might need a help of heating, ventilation and air conditioning (HVAC) contractor.

The EER stands for the energy efficiency rating. This value represents the rating of the air conditioner’s BTU over its wattage. For the illustration purposes, let imagine a 12,000-Btu air conditioner that is consuming 1,400 watts. The EER of this A/C is around 8.5.

The higher the EER figure, the better. However, the air conditioners with higher EER rating also come with an extra price.

Proper Size Of Your Air Conditioner

Proper sizing of the air conditioner will guarantee the best performance. Picking the right air conditioner with an adequate capacity for your room is the key to having the good climate in your room.

The too small air conditioner will make almost no difference to the air in your room. On the contrary, a loo large model will cycle on and off thus significantly increasing your utility bills. Moreover, an over-sized A/C will perform poorly on dehumidifying the air is going to be spoiled eventually.

Windows AC in an apartment block

Before purchasing a window air conditioner, you will need to measure the dimensions of the room, where you intend to place the A/C in. Then, multiply the length of the room by its width in order to get the square footage of the area. Then, you will need to match the room size with the rate of the BTU that is set for every air conditioner.

A rule of thumb: 20 BTU for each square foot is a standard figure. However, the climate you live in, the size of your window, the house shading and the height of the celling will affect the necessary number of BTUs for your room.

Small, Medium And Large Window Air Conditioner

The air conditioners operate at anywhere between 5,000 to 24,000 BTU per hour. Large air conditioners work at 10,000 - 12,500-BTU units per hour. They are able to cool up the room with 400 to 650 square feet area.

The conditioners that run at 8,000 to 10,000 BTU per hour are considered to be medium size models and can keep the room up to 450 square feet cool.

AC size

Small air conditioners are taking up anything between 5,000 to 7,000 BTU per hour while being able to cool 100 to 300 square feet room.

Key Window Air Conditioners Features

Window air conditioners come in different sizes, shapes, and colors. However, what really matters is the functionality of the device. Considering the wide assortment of the air conditioner models on the market, you will not be left hungry for the range of functions. In this section, we discuss the key features of the modern air conditioners.

Directional Vents

The directional vents are providing you with an opportunity to accurately control the flow of the air from the A/C with just a touch of the button. The feature allows focused cooling and the microclimate maintenance.

Most of the window air conditioner models have a number of directional vents for the precise cooling distribution for all of the room areas. Some models of the air conditioners have vents that can be adjusted to direct the flow of the air horizontally or vertically.

Directional Vents on AC

When choosing the air conditioner, take the layout of your room into the consideration. Go for the practical model that will be able to direct the airflow where you need it.

Moreover, the filters are not only great for removing the dust from the air, but they are also removing a number of other allergens, which is a great advantage for people with allergies.

Look for the air conditioners that have filters that are easy to remove. Regular maintenance of the vents will significantly extend the life of your window air conditioner.

Dehumidifying Mode

This feature comes in handy when you need to get rid of excess humidity in the room. Normally, people use dehumidifying mode during humid spring or fall days.

Efficiency Properties

A high-efficiency window air conditioner will definitely have the energy saving features. You can set the timer for when you want your air conditioner to be turned on/off. The energy saving feature is stopping the fan when the compressor is off. It is very convenient when you want to house to be fresh right before you arrive.

Inverter temperature

Programmable timer can set a delayed start or stop time, which is perfect for managing the energy consumption. Most of the air conditioners with timers offer the option to set the timer in one-hour intervals that normally go up to 12 or 24 hours.

Fresh-Air Intake Or Exhaust Setting

This feature of a window air conditioner is providing ventilation without cooling the air. The air is circulating in the room while keeping it fresh. This function is very useful for the times when you are feeling sick but you still want to have the fresh air in your room.

Remote Control

The remote control is one of the most basic and important features of the window air conditioner. This feature allows you to adjust the settings from any point of your room. Some of the window air conditioner models feature the built-in automatic temperature sensors that are regulating the room temperature by themselves.

AC LG Remote Control

Different Fan Speeds

The various speeds of fan allow you to have a superior control over the power of the airflow that is coming from the A/C. This feature is very convenient when you want the room to be fresh very quickly or, on the contrary, you prefer when the temperature is cooling gradually.

Energy Star Rating

We talked about the Energy Efficiency rating earlier in the previous section, Energy Star rating is telling you is able to operate up to 15 percent more efficiently than the item without this rating.

While choosing the air conditioner with Energy Star rating, you are able to save some money on the operational costs.

Temperature control

The thermostat feature of the air conditioner provides you with an opportunity to control the cooling process. Some of the middle and high-end models are offering a digital thermostat. It is including the unique readout of both the actual room temperature and the desired temperature (the one that was selected).

AC Temperature Control

Some of the industry experts say that the digital readout is more user-friendly. Moreover, these readouts are proven to be more precise in keeping the consistent temperature in the room.

These advantages of the digital thermostat are coupled with the automatic shut off feature. This function will automatically cycle the A/C on and off in order to sustain the desired temperature in the room.

Moisture Removal

Most of the window air conditioners that are present in the market are offering moisture removal function. Basic compression cycle air conditioners are removing the moisture through condensation. However, different models of A/C provide different usefulness at moisture removal.

Moisture Removal from Air

How Can You Measure The Effectiveness Of The A/C Moisture Removal Feature?

Moisture removal can be measured in different ways. One of such - how many pints per hour or liters per hour does one air conditioner extract from the air. For instance, medium sized 12,000 BTU window air conditioner normally removes anywhere between 3 and 4 pints of water in one hour.

Bear in mind that the higher the energy efficiency rating or seasonal energy efficiency rating is, the lower the ability of the air conditioner to remove the moisture from the air.

Sleep Setting

The sleep setting is a great feature that allows the air conditioner to operate at a very low setting during the night time. This is a great energy saving function that is able to keep the room fresh all night for the better sleep.

Sleeping comfortably with AC on

Control Panel

Control panel of the air conditioner is a very important aspect of the practicality of the device. The well-designed control panel is user-friendly and is a joy to use. Raised buttons with different shapes will help you control the A/C just by feel.

How Do You Install A Window Air Conditioner?

Window air conditioners are the perfect solution for the harassing heat in the summer months. Moreover, it is very easy to install. Now, we will go through basic steps of the A/C installation.

Size The Room

As I mentioned before, window air conditioners are coming in a variety of sized and their cooling capacities vary, too. Thus, it is important to choose the right A/C for your room. We have discussed the sizing of the room in the first section of our discussion when we talked about BTU and EER.

However, there is an alternative way to determine the right size of your air conditioner. You can use the air-conditioning calculator that is allowing you to just insert the dimensions of the room and get the result.

Size of the Room for AC

Moreover, there is a number of other factors that you need to consider for the proper sizing of your A/C. I mentioned before that you need to consider the climate of your room and shading of the house. In case you are planning to place the air conditioner on the shaded side of your house, decrease the BTU rating by 10 percent and vice versa.

Furthermore, if you are opting for kitchen air conditioner, you can add extra 4000 BTUs to the capacity requirements for your A/C. In case there are usually more than two people in the room, where you plan to put your A/C in, add 600 BTUs per person.

You will also need to think about your window size. Most of the A/C models are designed to fit in double-hung windows, yet there are units that are meant to be placed in the casement windows. Choosing the place for the window air conditioner is also very important since wrongly positioned A/C might block the way out in case of fire.


When your air conditioner arrives, don’t hurry to take it out of the box by yourself – you might want to get an additional hand for the process of installation. These devices tend to be very clumsy and you don’t want your new cool item to fall down straight after arriving at your house.

In case you have double-hung windows, installation could not be simpler. It might be necessary to assemble the extensions of the window unit – but some of the models have them already. Some other models may have special brackets for the window attachment.

If that’s the case, you will need to put those brackets in place beforehand. One of the important things – always check with the manual that came with the A/C.

Raise the lower windowpane, while your helper is placing the A/C on the windowsill. Then, slide out the air conditioner’s extensions that will fill the empty window space. Afterward, level the unit as it is stated in the manufacturer’s manual. Most of the A/C models should tip slightly to the outside for the draining purposes. However, some of the models are not designed to tilt.

The next step – fasten the A/C to the brackets or lower the windowpane onto a unit in order to fix the item in the place. Most of the models will make you secure the upper windowpane into place in order to prevent movement.

We are almost done! Next, secure the extensions to the window jamb. Now you can seal the A/C. For the indoors sealing, use weatherstripping that is provided by the producer. On the outside, you can use calk on the perimeter of the item for the better seal.

Finally, plug the device in and you are good to go!


These days, air conditioners emerge as a necessity not only in the hot countries but also in typical inland climate countries. More than 6.5 million air conditioner window units are sold each year.

Window AC in an apartment

A/C is a great way to cool the room without having to pay for the pricey central air conditioning system. Moreover, these devices provide numerous useful functions that will make your life so much easier.

Now, when you know pretty much everything about window air conditioners, it is high time to understand how to choose the perfect one for your house with the help of our Best window air conditioner Buying Guide.

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