Window air conditioner units are the most popular type of air conditioner in the US. When you consider that 84% of homes have some sort of air conditioning, this is a vast market. Basically, about a third of households have a window air conditioner of some type. So, let's take a closer look at the humble window air conditioner to give you the lowdown on the facts, so that you can make an informed choice.

How Does a Window Air Conditioner Work?

A window air conditioner draws warm air from the room and passes it through a coil. The refrigerant in the coil captures the hot air, which is expelled outside through the vents, leaving the cooled air to circulate back into the room. There is another plus-side to window air conditioner units; they remove humidity from your room. The coil gets extremely cold when it removes the warm air, and moisture condenses on the surface. Imagine a glass of ice-cold soda, and you’ll get the picture. This water is then channeled through an outlet pipe and drained outside.

Is Refrigerant Safe?

There are two types of coolant in use in the United States. Before 2006, window air conditioner units used ozone-depleting R-22 refrigerant which was highly-damaging to the environment. To put it into perspective, R-22 is 2,000 times more potent than carbon dioxide. Which is a lot.

• R410A - This is ozone-friendly and chlorine-free, so it's far safer than R-22. But it does have a global warming potential. R410A is the new 'default' refrigerant for a lot of HVAC manufacturers, and that includes window air conditioner producers. Most of the units you'll find use R410A.
• R-32 - This is the new kid on the block and the latest in refrigerant technology. It has a global warming potential of 675, three times lower than R-410A. R-32 also has zero impact on the ozone layer and is 10% more efficient. But there is a downside; expect to pay more for units that have R-32 coolant, since it is so new.

Is A Window Air Conditioner Noisy?

Most window A/C units operate at around 60-85 dB. How loud is that? A vacuum cleaner generates noise levels of about 75 dB, so a window air conditioner is noisy when compared to central units and split systems. The two loudest components, the fan and the compressor, are located inside the unit sitting on your window ledge, and that creates the noise. In split systems, the compressor is located outside. That means it can be placed far away from where you're trying to relax. The good news is that modern window air conditioner units are getting quieter. Better design and advancements in technology are delivering these changes. Still, they are the loudest of the bunch when it comes to modern air conditioners.

Is A Window Air Conditioner Energy-Efficient?

A window air conditioner is rarely as efficient as a central or mini-split air conditioner. The necessity of their compact size means that making a window air conditioner high efficiency can get very expensive. But, this isn't always true. There are some, relatively speaking, energy efficient window air conditioner units. But how do you know? Check the EER.

• EER - This is the measurement of the air conditioners efficiency when the room temperature is 95 degrees Fahrenheit. EER is often considered the baseline efficiency of a particular unit.
• SEER (Seasonal Energy Efficiency Ratio). - This measurement is applied to central A/C systems and is usually higher than EER because the measurement period is more prolonged and factors in a broader range of temperatures. Roughly speaking, SEER measures air conditioner performance over a cooling season.

What Size Window Air Conditioner Do I Need?

Most window air conditioner units have a BTU (British Thermal Unit) capacity of between 12,000 and 36,000. So, at the lower BTU scale, 12,000 should handle rooms of 350-400 square feet, and at 36,000 BTUs, it is capable of cooling spaces in excess of 1,500 square feet. When you compare window A/C units and their capacity to central or split systems, the difference is stark. A split or central air conditioner has a maximum cooling capacity of over 60,000 BTUs.

Why Choose a Window Air Conditioner?

It may be that you live in an apartment, and a window air conditioner is your best option. In New York, 75% of the buildings in the five boroughs are pre-1960s, which means retrofitting air conditioning is expensive and impractical. Also, city laws allow residents to fit units up to a maximum of 36,000 BTU without a permit. As most New Yorkers are apartment dwellers, window air conditioners are the obvious choice. Window air conditioners are also ideal if you want to use zone cooling in your home. It is a way of keeping rooms that are occupied cool while saving energy and money by not conditioning the air in the unoccupied parts of the house. Also, you may not have the funds for a split or central system. A window air conditioner is an ideal choice because it is relatively cheap to buy and easier to fit. Someone with basic tools can install one in less than an hour in many cases. If you compare that to the cost of a retrofitted central air conditioner, the upfront cost savings are tremendous. Plus, if you live in a rental home, a window air conditioner is the perfect way to get cool air without damaging the fabric of the building.

How Much Does A Window Air Conditioner Cost?

You can pick up a cheap window air conditioner for as little as a couple of hundred dollars. However, if you want a bells and whistles model, expect to pay over $1,000. The 18k BTU 10.7 EER Friedrich Kuhl Air Conditioner Window Unit is an excellent example of a high-end window air conditioner.

The Pros and Cons of A Window Air Conditioner

Pros	Cons
The unit costs are much cheaper Virtually no installation costs Better for smaller homes Cheaper replacement costs Cools the occupied rooms only Saves you money on energy costs No retrofitting costs Better for apartments	Only cools one space at a time Looks ugly Blocks light Possible security risk Water staining may occur Can be noisy Some models are very inefficient

What to Look for in a Window Air Conditioner

• BTUs - BTUs are crucial when trying to select the right size window A/C unit to match your space. Get it wrong, and the unit will struggle to keep you comfortable. For example, an 18k window air conditioner is typically used for 750 square feet. If you have 750 square feet, don't get a 9k unit.
• CFM (Cubic Feet per Minute) - CFM is the air volume that the unit will generate per minute. A higher CFM rating indicates a stronger air flow.
• Antimicrobial Filters - Look for an A/C unit that has these filters. They clean the air that passes through the coils, increasing the health benefits to you and your family. Also, look for a filter alert that warns you when the filter is dirty.
• Remote Control - Having an A/C unit that works by remote control means you never have to leave your seat to adjust the settings.
• Programmable Thermostat and Timer - Having the ability to program the settings in advance for each day means that you get a more comfortable environment and an efficient machine. And it will turn on and off at your preset times.
• Digital Controls - Most A/C units have these, but if you are buying on a tight budget, you might have to accept basic, manual controls.
• WiFi - Some window air conditioning units have WiFi enabled controls that allow you to set the unit via an app on your smart device.
• Auto-Restart After Power Outage - If the power cuts out, having an auto-restart function means the unit will power back up when the electricity comes back on. It also stays at the original settings, saving you time reprogramming the unit.
• Economy Mode - This enables the air conditioner to run using less energy.

Climate Considerations for A Window Air Conditioner

The USA is divided into zones based on climate, proximity to the sea, and elevation. Zone 6 and 7 cover states like Alaska, where the winters are extremely harsh, and the summers are cooler. If you live in a northern state, you are unlikely to need a high capacity window air conditioner. In these circumstances, you might get away with a cheaper model that only costs a couple hundred bucks.

Final Thoughts

Window air conditioner units can be an excellent choice when you accept that they work best for single-zone cooling. They are low-hassle, easy to fit, simple to operate, and, above all, cheap to buy. Unfortunately, they are often quite energy IN-efficient in order to push the individual unit cost down as low as possible. With 5% of all electricity usage in the US attributed to A/C units, costing consumers over $11 billion every year, it is imperative that energy efficiency is at the top of your priority list.

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