Window air conditioners are an economical way to cool your room
If you want to cool off a bedroom, living room or office, a window air conditioner is a great solution. The initial unit costs less than a central air conditioner or a portable air conditioner (covered in their own reports), and a room air conditioner runs on less electricity than both. And while central air conditioners are thought to be more energy-efficient overall, in fact, experts say that if you only want to cool one room at a time, especially for specific time periods, a room air conditioner can be a much better choice.
Window air conditioners operate on basic refrigerant principles: extracting warm air from a room, circulating that warm air over a coil that is filled with refrigerant to make it very cold, converting that heat into vapor, then blowing the heat to the outside and the cooled air to the inside. These units are meant to be temporarily mounted on your window sill for use in hot weather, although some people just leave it in the window year ‘round. Of course, in cold climates this means you may experience heat loss from that room.
Installing most window air conditioners is pretty straightforward: open the window, set the unit on the ledge and close the window. The top pane of the window helps hold the air conditioner in place. Plastic curtains, which come with the air conditioner, slide out to the sides of the window. These, along with a little foam tape, seal around the air conditioner to keep hot air and debris from sneaking in through the cracks and keep more of your cold air in the room. Screws, sash locks and, in some cases, sill supports, secure the unit to eliminate any chance of it falling out and causing possibly catastrophic damage to persons or property.
There are two types of standard window air conditioners. Most are one-piece units, but others feature a slide-in chassis. Installing a unit with a slide-in chassis is a little more involved, but is also easier because you don't have to wrestle with the full weight of the air conditioner as you put it in place in your window. Instead, you install the outer sleeve first and then, with that securely in place, slide in the air conditioner itself.
Casement window air conditioners are a special case. For windows that slide to the side or are hinged, there are two options for window air conditioners. The first is to buy a regular window-mount unit and custom fit a piece of wood or Plexiglas to cover the opening above the air conditioner. The second is to get a casement air conditioner. These are tall and skinny, and often include curtains that extend above the unit to seal the opening. Casement air conditioners tend to be more expensive than traditional window air conditioners with the same cooling capacity, but sometimes fit better in the window. These units also aren't as common as traditional air conditioners -- none of the expert tests include casement air conditioners in their comparisons, and few models have a significant number of owner reviews to accurately gauge performance.
What about through-the-wall air conditioners?
If window mounting an air conditioner isn't convenient or aesthetically desirable, you can choose to mount a room air conditioner through a wall. Some window air conditioners with slide-in chassis can be mounted this way, and some room air conditioner models are designed exclusively for in-wall mounting. Through-the-wall air conditioners work the same way as window air conditioners, but their installation is both permanent and more complicated. Homeowners with good DIY skills might be able to handle the job on their own, but others would be best served by hiring a professional installer. In wall room air conditioners also are more likely to run on 220 or 230 volts, in which case you may also need an electrician.
User feedback on dedicated through-the-wall room air conditioners is scant, and we spotted only a couple of choices with more than a handful of user reviews. In a free article, ConsumerReports.org says that unless you are looking to replace existing through-the-wall units, a window air conditioner is the better option as there are fewer choices among through-the-wall models, they are more costly to buy and install, and the way they are installed can make them less energy efficient.
Getting the size right
Room air conditioners are grouped by their cooling power. This is measured in British thermal units (BTUs). The higher the BTU, the more powerful the air conditioner. To find the right size for you, the first step is to match the square footage of the room you want to cool to the correct BTU. You then need to adjust for various factors such as whether the room is sunny or shady, the number of occupants typically in the room, and whether or not the room is used as a kitchen. The folks at EnergyStar.gov have put together a handy guide that provides BTU for different sized rooms, shows how to properly measure a room, and provides correction factors for various situations.
When shopping for a new air conditioner, experts say the most common error shoppers make is to purchase the wrong size unit for their space. If it's underpowered for the space, it will have to work too hard to cool the air properly. If it's too large, it will turn off before the room is adequately cooled and dehumidified. Generally speaking, window air conditioners (as well as through the wall models) can be divided into three broad categories:
Small window air conditioner: Also called mini air conditioners, this size is the lightest and least expensive. With cooling capacities of 6,000 BTU and under, these are designed for rooms up to about 250 square feet.
Medium window air conditioner: Ranging from about 7,000 to 8,000 BTU, these are ideal for rooms between 250 and 350 square feet.
Large window air conditioner: A large air conditioner with 9,000 or higher BTU has enough cooling power for rooms 350 square feet and above.
Finding the best window air conditioners
To find the best air conditioners, ConsumerSearch looks first at professional tests. In those, experts compare different units in side-by-side tests to determine cooling performance, noise levels and the ability to operate in low power conditions. From there, our editors evaluate owner reviews for real-world insights into which window air conditioners are easy to install, user-friendly and reliable. We then distill all of that information to find the Best Reviewed window air conditioners for any sized room and budget.
One challenge this year was that new energy efficiency rating (EER) standards went into effect at the end of 2015, raising the minimum efficiency at which a window air condition can earn Energy Star Certification, from 11.2 EER to 12 EER. This means that some air conditioners that were Energy Star Certified last year are no longer qualified to earn that label. However, that was not a top factor in our choices, simply because experts note that the difference between 11.2 EER and 12 EER only represents a few dollars of savings over a year, and, even though the AC units may be given identical decibel ratings, more energy efficient air conditioners tend to earn poorer marks for noise in professional tests. With the exception of the small air conditioner category (due to the unavailability of many new AC units) in categories where we did not choose an Energy Star Certified model as our Best Reviewed, at least one of our runners up earns that designation, giving our readers the option of slightly less noise or slightly better energy efficiency.