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 large whole-house air conditioner or a portable air conditioner, and a room air conditioner runs on less electricity than both.
Window air conditioners are installed in a window. It temporarily mounts on your window sill, cooling down the room it's placed in. On the front of the unit -- which faces into the room -- is a grill to pull in air, which gets blown out through vents. The best designs let you adjust louvers on the vents to aim the cool air where you want it. The back of the air conditioner hangs outside, with silver fins that help keep the unit from overheating but don't draw air into the room. Window air conditioners also pull excess moisture out of the air as they lower the temperature. By bringing the humidity down, the room becomes more comfortable and less sticky. This excess moisture evaporates or drips out the back of the unit.
Installing most window air conditioners is pretty straightforward: pen 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.
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 at 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.
Spending more money on an air conditioner doesn't necessarily guarantee a better appliance. According to reviews, several budget-priced options still have excellent cooling performance. More expensive units often include extra convenience features, however, such as a timer and remote control. For many owners, these are worth the additional cost. All of the air conditioning units in our report are 115 volts and plug into a regular household outlet.
For an air conditioner that is even more temporary than a window unit, can be moved easily and doesn't block the view, consider a portable air conditioner, which we cover in a separate report. If you want to cool more than one room at a time, read our report on central air conditioners.
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.
Elsewhere in this report:
Best AC for Small Rooms | Best AC for Medium Rooms | Best AC for Large Rooms | Buying Guide | Our Sources